• Welcome to the DeeperBlue.com Forums, the largest online community dedicated to Freediving, Scuba Diving and Spearfishing. To gain full access to the DeeperBlue.com Forums you must register for a free account. As a registered member you will be able to:

    • Join over 44,280+ fellow diving enthusiasts from around the world on this forum
    • Participate in and browse from over 516,210+ posts.
    • Communicate privately with other divers from around the world.
    • Post your own photos or view from 7,441+ user submitted images.
    • All this and much more...

    You can gain access to all this absolutely free when you register for an account, so sign up today!

Too Deep, Too Often, Too Soon?

Thread Status: Hello , There was no answer in this thread for more than 60 days.
It can take a long time to get an up-to-date response or contact with relevant users.
I have done scooter dives before. Aside from terrible DCS risks, the high speed ascent can create extreme dizziness during the ascent, and at the surface after the dive. The reason is hypothesized to be unequal equalization of the inner ears during the ascent. In other words, air seeps out of the eustachian tubes at different rates during the high speed ascent, causing one ear to be more pressurized than the other, leading to dizziness, and this could also create other weird feelings in your head.

Other than DCS and reverse ear blocks, scooters can create other risks. Using a high speed scooter, I nearly knocked myself out cold as I ascended from a wreck. I hit an overhanging beam from the wreck, straight on top of my head, at high speed. I got crazy dizziness and wooziness from the hit, but thankfully I didn't get knocked out cold.

I don't use scooters anymore -- their only use in my opinion is to cover huge distances on the surface when trying to reach islands or other offshore dive sites.
 
Hello Eric,

Thank you for contributing your experiences and perspectives on this. They are quite helpful. When you say high speed, which DPV(s) or rough speed would you guess you were traveling at? It makes sense that rapid ascent could contribute to problems like those you mentioned, perhaps even more over time and across a variety of divers. Uneven equalization on ascent is a factor that wouldn't have occurred to me.

Your experience on the wreck is a telling one. It is great that you weren't knocked out despite the solid impact. Helmets are standard kit for cave and some wreck divers, it makes sense that guys on a DPV would want to have a good lid on around confined areas. I haven't used one diving in some years. Despite that, I could imagine hitting hard enough to where a low bulk/drag helmet might not even completely avoid creation of a serious problem.

Here I was thinking my old wimpy Sea Doo VS dive scooter was too slow but it may have been an asset in reality. It is noticeably slower than my old Techna and far slower than a Remora. Allowing extra time for gas exchange and processes appears to be a good thing.

Anyway, I follow your point about special hazards posed by scooter free diving and respect your choice to move on from it except for use in extended travel.

Please keep the comments and observations coming in as I suspect there may be additional hazards and special considerations beyond those listed so far.

Rick
 
Last edited:
The 'fast' scooter I was using was a giant orange Farallon scooter (don't know the model). The thing weighed something like 100lbs out of the water.

I think I was traveling around 3m/s peak speed. I was able to scooter down to 35m, and circumnavigate the entire HMCS Mackenzie wreck on a single dive, then rocket back to the surface. I'd estimate the total distance of about 320m in 3 minutes. However, I was not traveling at top speed the whole time.
 
well now you are not alone in that club lady of the lake - thanks so much for sharing your story- it helps me answer these nagging "why's" that have been roaming around my head.

also of note to everyone, i have been doing alot of rsch since this happened (am going to a advanced decompression physiology course offered at USC next wknd too because i felt the MD's i spoke with didn't have enough precise info) but in my research i also found an obscure 2006 DAN study that was conducted by a control group of recreational wesuit divers in the caribbean, cold water divers in dry suits, and US navy divers in dry-suits that purposefully held warm water.


the net net of the study was that warm skin in warm water CONSISTENTLY absorbed significantly greater amounts of nitrogen at depth!

that was the other variable on my trip - the water was HOT! 88 degrees farenheit and i was hot the whole time too.

i'm feeling more sure that i was actually experiencing DCS (even though it took 3-4 days to manifest symptoms) and that i was not only absorbing more nitrogen than usual but that i compounded it with my freediving after scuba.

thanks much to you Jon and Sam for your insights - tis much appreciated.:inlove

kp

Kelp princess, the study on DCS was on scuba only? Accumulation of N2 during scuba diving in warm water was more than in cold water?

I don't do any scuba, but the temperature effect is very interesting to me. I research repetitive free diving in water which is hot at the surface but quite cool at depth say at 20 - 40 feet deep or more, no wetsuit.
DDeden
 
Kelp princess, the study on DCS was on scuba only? Accumulation of N2 during scuba diving in warm water was more than in cold water?

I don't do any scuba, but the temperature effect is very interesting to me. I research repetitive free diving in water which is hot at the surface but quite cool at depth say at 20 - 40 feet deep or more, no wetsuit.
DDeden

hi - yes the study was conducted by DAN, and since i was completely unsatisfied with what their hotline attendants were saying,
i did a little more reconnaissance and here's what their chief PhD who ran the study wrote to me, and I quote:

"We do not have formal recommendations for freediving before or after compressed gas diving. The most important reason is that we simply do not have the data to make an evidence-based recommendation. You can, however, read some fairly interesting discussion of the question in the open discussion at the 2006 breath-hold meeting sponsored by the Undersea and Hyperbaric Medical Society (UHMS) and DAN. The published proceedings are available from both DAN and UHMS.

I can give you a nutshell version of the discussion. Scientific diving standards specify no freediving after compressed gas diving. There is some frustration in the community because of the lack of evidence one way or another. Some freediving educators recommend freediving and compressed gas diving only on different days or applying the DAN flying after diving guidelines to freediving after diving as a simple set of rules. There is a much greater theoretical risk of freediving after compressed gas diving than freediving beforehand. The level of risk produced by freediving will be influenced by the magnitude of the pressure profile of the freedive. Extreme profiles will include some inert gas uptake and may promote the arterialization of bubbles otherwise trapped in the lungs. Very shallow freediving undoubtedly poses much less risk, but we do not have enough data to comment on the absolute risk. We try to base recommendations on evidence but, pending the collection of relevant data, applying the flying after diving rules to freediving after diving may be reasonable.

The temperature issue is also not a simple one. Most importantly, water temperature alone is of virtually no value. Thermal stress and status is a function of the protective equipment. The right protection can do a lot to obviate external conditions. Thermal stress as measured at the skin may one day provide valuable information for modeling decompression stress. This, though, is going to require a skintight suit with many sensors and a lot of research data that we do not have now. We need the available technology to advance a little further and then the funding to begin to reconcile the information with reality. One parameter of required data is the relationship between perception and physiological status. One person's 'hot' during diving can be very different from that felt by someone else. It is fairly easy to discuss theoretical risk but much more difficult to produce the evidence. The awareness exists, though, so progress will be made in our understanding.

Your comments are appreciated. We would all like to see more data and greater understanding and frequently share frustrations like those you expressed. We will always try to help where we can but I think that we will always have more questions than answers.

I hope this helps."


Neal W. Pollock, Ph.D.
Divers Alert Network
6 West Colony Place
Durham, NC 27705

Although, Neal refers to a breath holding study above this is not the study that informed me of water temps - the study i am referring to is also a DAN study and it measured the thermal temps of various types of scuba divers in various exposure suits and various water settings, even a set of US Navy Divers with warm water intentionally filled in their dry suits.

I am happy to email you a copy of the PPT if you are interested.
I think it might live on the DAN website too - but more importantly if thermal stress is an ideal environment for absorbing N2 for scuba divers then I would extrapolate that it would affect freedivers as well.

I will also let ya'll know what I hear/learn from the NASA PhD after this wknd's class.

kp
 
Hi kelp princess,

to go off an a tangent:

to briefly explain my interest, I think human ancestors a million years ago dove daily for food (clams etc.) at tropical seashores, which is why we don't look like our closest genetic cousins the chimps. These human seashore ancestors did not hyperventilate before diving, did not pack or wear fins, masks or scuba and their "wetsuit" was the under-skin layer of "bioprene" fat seen on humans (babyfat) but not other primate kin. They dove alternatively in male-female diving teams; while one backfloated above in the very warm sunlight lagoon surface water, the other dove down into the cool dark blue along reefs collecting sessile shellfish, repeating this over and over, switching roles, until they got their fill of seafood, then went back to the beach for a coconut cocktail.

This would require that at depth, the water was cool, not hot, otherwise the [MDR] Mammalian Divers Reflex would not engage, which means oxygen would not be conserved well. The MDR was an essential energy-saving part of the dive cycle; whereas during backfloating at the surface the opposite occurred, Uncertain on details, may be wrong: "wasting" [O2] oxygen in order to remove excess [N2] Nitrogen and [CO2] Carbon Dioxide and accumulated waste products. Urinating during the dive, and sweating at the sunny surface removed urea (which contained Nitrogen), and humming at the surface removed [NO] Nitric Oxide from the sinuses (killing waterborne bacteria in the water which was allowed into the nasal/sinus/middle ear cavities during the dive to avoid equalizing constantly). This humming at the surface by the backfloater (likely with a chest-held infant that was clinging to the long head hair and female's breast or male's beard) was the first lullaby, the NO-enriched air was inhaled by the infant (who could not hum until later with the first word "mmamma" and could not yet shed anti-biotic tears, so the parent's NO provided antibiotic protection to the infant's face), and the humming could be heard by the dive partner below (not distracted by noisy scuba bubbles), who then made tongue clicks which was heard by the backfloater, this "hydrosonic" communication was the original form of sustained speech, (which later derived into the vowels and consonants) allowed non-visual contact between the partners, the sound waves carried efficiently through water and the very dense occiput (the skull plate on back of head which in ancient humans was the most dense bone in the body, perfect for sound transmission via bone conduction as found in dolphins and sea cows).

So, "too deep, too often, too soon", according to the archaic diving cycle was not an issue, as long as the diving partners alternated consistently, allowing gas exchange at the surface. I assume max depth was possibly 100 m, but much more likely 30m max for adult males, 15m for females repetitively, and probably often less. No diving in fast current, cold surface water, hot depth water, big surf or rainy weather.
[They don't teach all this in kindergarten or sunday school, but I think it's accurate.] :)

DDeden
 
Last edited:
This humming at the surface by the backfloater (likely with a chest-held infant that was clinging to the long head hair and female's breast or male's beard) was the first lullaby, the NO-enriched air was inhaled by the infant (who could not hum until later with the first word "mmamma" and could not yet shed anti-biotic tears, so the parent's NO provided antibiotic protection to the infant's face), and the humming could be heard by the dive partner below (not distracted by noisy scuba bubbles), who then made tongue clicks which was heard by the backfloater, this "hydrosonic" communication was the original form of sustained speech, (which later derived into the vowels and consonants) allowed non-visual contact between the partners, the sound waves carried efficiently through water and the very dense occiput (the skull plate on back of head which in ancient humans was the most dense bone in the body, perfect for sound transmission via bone conduction as found in dolphins and sea cows).


now that's some crazy anthropological info!

i'm buying most of it but since i can't make cloud clicking sounds with my tongue while having the ease of air around - i can't imagine being able to do it loud enough UW for someone's skull plate to feel the reverberation.

perhaps those folks had larger sinus cavities and mouths as well?

kp
 
now that's some crazy anthropological info!

i'm buying most of it but since i can't make cloud clicking sounds with my tongue while having the ease of air around - i can't imagine being able to do it loud enough UW for someone's skull plate to feel the reverberation.

perhaps those folks had larger sinus cavities and mouths as well?

kp

Neandertals living on the coasts had huge sinuses. According to some anthropologists, their voices (according to fossil anatomy, hyoid bone structure) probably had somewhat high-pitched during speech compared to modern folks.

Perhaps their mouths were larger (they lacked chins), I don't think that would matter so much. I think their visible external ears (pinnae) were smaller than ours, maybe even smaller than gorilla or gibbon ears, but pinnae don't fossilize so it's unknown.

Still water carries sound far far better than air does, that's why both dolphin clicking and humpback whale song can be heard at long distances. For the same reason, solid flat ground (savanna) carries sound. Bull elephants make thunderous bass trumpeting sounds that carry for miles, the females hear the sounds through their FEET via bone conduction from the solid ground, NOT primarily through their huge external ears via air conduction. Air simply doesn't carry sound very effectively. Human hearing is 50% air conduction, 50% bone conduction. In water, only bone conduction functions.

As long as the backfloater is on the still surface with the ears and occiput in the water, and the entire ear (inner, middle and outer ear) is fluid filled (in a lagoon, not in open sea with loud surf), and the diver's ears are also fluid filled, any clicking or humming sounds will carry a good distance. In air, clicking doesn't carry very far, (though the Khoisan people retain clicks in their language), but dolphins prove that UW clicking is both effective and efficient communication.

The problem with hearing UW is presence of air in bone cavities, once air is replaced with water, sounds carry well, no need for loud clicks, even soft clicks carry a ways. Simply ticking the teeth together works too for a short distance. Some shrimp, crabs and fish make clicking sounds in various ways. There's no loss of air in clicking, unlike vocal speech or humming.

Caution, this stuff is potentially DANGEROUS if you don't know what you're doing. It's still just theoretical, I haven't tested it yet, being poor and stuck in Nor Cal by cold water, I need to get down to the tropics to do empirical research.

Any rich uncles or aunties wanna donate to research, lemme know!

Still workin ... :)

DDeden
 
Last edited:
whereas during backfloating at the surface the opposite occurred, "wasting" [O2] oxygen in order to remove excess [N2] Nitrogen and [CO2] Carbon Dioxide and accumulated waste products. Urinating during the dive, and sweating at the sunny surface removed urea (which contained Nitrogen), and humming at the surface removed [NO] Nitric Oxide from the sinuses (killing waterborne bacteria in the water which was allowed into the nasal/sinus/middle ear cavities during the dive to avoid equalizing constantly).
Do you mean that the NO and urine remove excess Nitrogen that was absorbed from air?
If so then I don't see how that is possible, N2 is inorganic and needs to be "fixed" inorder to be metabolized, as far as I know mostly unicellular organisms have Nitrogen fixiation capabilities and we definitely don't... and I doubt symbiotic bacterias can produce enough during diving for it to make any difference....
 
Do you mean that the NO and urine remove excess Nitrogen that was absorbed from air?
If so then I don't see how that is possible, N2 is inorganic and needs to be "fixed" inorder to be metabolized, as far as I know mostly unicellular organisms have Nitrogen fixiation capabilities and we definitely don't... and I doubt symbiotic bacterias can produce enough during diving for it to make any difference....

Hi Deep Thought, thanks much for checking.

I erred, mixing (apples) inert N2 from air, and (oranges) Nitrogen compounds from high protein molluscs. I'd thought that N2 was not easily absorbed into blood, that scuba at depth increased absorption, but that a significant part came from high-protein foods, and that adding N2 at depth was just a part of it, the straw that broke the camel's back.

Do you know whether, upon switching from inhaling air to O2, does blood N2 drop down to zero? If so, would digestion of hi-protein food rich in nitrogen compounds (molluscs) cause an increase in N2 in the body, especially in the blood? That is what I thought happened, which is why I thought of excretion. I was thinking of other chemicals which end in the bloodstream (drugs etc.).
Anyway, I'll review and edit my post, for now i'll just box it off.
Yes, I know, i need to take a course or 3. If only...

Note on NO production sources: From Wikipedia:

"In the body, nitric oxide (the 'endothelium-derived relaxing factor',
or 'EDRF') is synthesized from arginine

[ame=http://en.wikipedia.org/wiki/Arginine]Arginine - Wikipedia, the free encyclopedia[/ame] and oxygen
[ame=http://en.wikipedia.org/wiki/Oxygen]Oxygen - Wikipedia, the free encyclopedia[/ame] by various nitric oxide synthase
[ame=http://en.wikipedia.org/wiki/Nitric_oxide_synthase]Nitric oxide synthase - Wikipedia, the free encyclopedia[/ame] (NOS) enzymes
[ame=http://en.wikipedia.org/wiki/Enzyme]Enzyme - Wikipedia, the free encyclopedia[/ame] and by sequential reduction of inorganic nitrate."
(dang complex biochemical pathways!!)

DDeden
 
Last edited:
The problem with hearing UW is presence of air in bone cavities, once air is replaced with water, sounds carry well, no need for loud clicks, even soft clicks carry a ways. Simply ticking the teeth together works too for a short distance. Some shrimp, crabs and fish make clicking sounds in various ways. There's no loss of air in clicking, unlike vocal speech or humming.
Totally OT now, but I am not sure about the role of air in underwater hearing. The most advanced orders of fish, Cypriniformes (carp, minnows, most coarse fish, danios, loaches etc.), Characiformes (tetras), Siluriformes (catfish), and Gymnotiformes (electric eels, knifefish), have a series of bones connecting the air bladder to the inner ear, allowing them to hear a much wider range of sounds than other fish. This must be important, because species which no longer need an air bladder for buoyancy (catfish, loaches), still have a small one for hearing, and in some cases for producing sounds.
 
Do you know whether, upon switching from inhaling air to O2, does blood N2 drop down to zero?
In other words, you're asking if we can off-gas N2 to zero or is there some minimum N2 level in the blood due to metabolic production?
AFAIK most of our nitrogenic waste products are oganic (Amonia+CO2=Urea) and urinating is the primary way of getting rid of it. If I remember correct there are some biochemical reactions in our body that create N2 as a byproduct, but they are not a primary mean of getting rid of excess Nitrogenic compounds, if that was the case then we could've just exhaled N2 all the time and not need to pee.
If so, would digestion of hi-protein food rich in nitrogen compounds (molluscs) cause an increase in N2 in the body, especially in the blood?
From the reasons I mentioned above I tend to guess that the change would be very minimal if at all.
But it's just an estimation based on my incomplete knowledge.
By the way, NO is also a vasodilator.
 
Hi Deep Thought, thanks much for checking.

I erred, mixing (apples) inert N2 from air, and (oranges) Nitrogen compounds from high protein molluscs. I'd thought that N2 was not easily absorbed into blood, that scuba at depth increased absorption, but that a significant part came from high-protein foods, and that adding N2 at depth was just a part of it, the straw that broke the camel's back.

Do you know whether, upon switching from inhaling air to O2, does blood N2 drop down to zero? If so, would digestion of hi-protein food rich in nitrogen compounds (molluscs) cause an increase in N2 in the body, especially in the blood? That is what I thought happened, which is why I thought of excretion. I was thinking of other chemicals which end in the bloodstream (drugs etc.).
Anyway, I'll review and edit my post, for now i'll just box it off.
Yes, I know, i need to take a course or 3. If only...

Note on NO production sources: From Wikipedia:

"In the body, nitric oxide (the 'endothelium-derived relaxing factor',
or 'EDRF') is synthesized from arginine

Arginine - Wikipedia, the free encyclopedia and oxygen
Oxygen - Wikipedia, the free encyclopedia by various nitric oxide synthase
Nitric oxide synthase - Wikipedia, the free encyclopedia (NOS) enzymes
Enzyme - Wikipedia, the free encyclopedia and by sequential reduction of inorganic nitrate."
(dang complex biochemical pathways!!)

DDeden

Hi pal,

Nitrogen is considered an inert gas. It can not be metabolised / utilised from the human body. It is only absorbed, distributed and disolved in the body tissues according to the pressure difference in the alveoli and in the blood in the lung vessels. When this pressure is reversed the excess Nitrogen starts to off-gasing i.e. return to the alveoli from the blood and gradually from all other tissues back in the blood and alveoli. The main driving factor is again the pressure gradient.

Definitely if one breath pure oxygen for several days the blood Nitrogen would drop to zero but before that one would suffer a condition called pulmonary oxygen toxicity.

Nitrogen is also a part of almost all biomolecules but that is something different than gaseous nitrogen. The nitrogen containing byproducts of metabolism do not include gaseous nitrogen.
 
Last edited:
Totally OT now, but I am not sure about the role of air in underwater hearing. The most advanced orders of fish, Cypriniformes (carp, minnows, most coarse fish, danios, loaches etc.), Characiformes (tetras), Siluriformes (catfish), and Gymnotiformes (electric eels, knifefish), have a series of bones connecting the air bladder to the inner ear, allowing them to hear a much wider range of sounds than other fish. This must be important, because species which no longer need an air bladder for buoyancy (catfish, loaches), still have a small one for hearing, and in some cases for producing sounds.

Do most of those fish live somewhat amphibiously, compared to pelagic ocean fish? If so, air conduction would be significant, as it is in frogs and seals. AFAIK most ocean pelagic fish have one inner bone connected to the inner ear, while mammals have three. (I'd guess sharks have none). Do you know for certain that these (catfish, loaches) fish while at depth have air-filled bladders connected to their ears? Can the bladders empty at depth, (or fill with water or oil) and then refill with air at the surface? It is also possible that their ears are functionally deaf at depth but they pick up (hydrosonic) vibrations via their lateral line and/or bones.

I think there's a freshwater fish that squirts water up at flying insects, I would guess that fish has good air-conduction aural capabilities (ear-air-sac), but also good water-conduction aural capabilities.

o0O0o0O0o0O0o `<8{(((>< o0O0o0O0o0O0o

Regarding hearing underwater Too Deep, Too Often and Too Soon; although I think that ancestral humans dove at equatorial seashores in warm surface water, I've no doubt they encountered cool to cold water at depth and especially during coastal migrations farther from the equator. Evidence of ear exostosis (bony ear canal rings) has been found in a number of human fossils (Upper Nile River, Peruvian coast, Rome coldwater baths), this occurs due to sustained periodic exposure to cold water in the external ear canal over time.

I think exostosis indicates mostly youthful single males habitually competing at greater depths without sufficient surface intervals to warm the ear canal and cerumen, over time this would produce bony accretion around the canal. This may indicate spearfishing more than mollusc hunting, since spearing requires a longer time at depth. However the fact that humans are no where nearly as hydrodynamic mammals like dolphins, sea lions, etc. indicates that spearfishing or "fast" chasing pelagic fish was not as common as "slow" diving for sessile/benthic foods (molluscs, oysters, marine snails, etc.). I'd guess spears were more jabbing-thrusting-prying tools, rather than shooting weapons; useful for crabs, flounder, immobile camoflaged octopi and such.

AFAICT, paired archaic divers backfloated/dove in rotation at warm sunlit surface, the middle ear was warm-water filled and the external canal also warm-water filled, the earwax kept this warm water in place during the dive into the colder depths when the MDR was engaged, acting like thermal ear-plugs but not air-holding ear plugs.

Although yet unconfirmed, I feel quite certain that simultaneously a similar thermo-retention system was employed in the sinunasal cavity and affiliated middle ears (via the eustacian tubes) by allowing warm surface water (larynx was valved shut) in and then closing the nasal passage via the swollen tissues of the inferior concha (VR) and/or philtrum closure (both of these are found only in humans, not our arboreal kin) early during the dive into the cooler depths, preventing the "sinus-ice cream headache" otherwise sure to affect the diver (and which is now often covered by mask or hood) and alleviating the need for continuous equalizing with each elevation/pressure gradient.

Ear extoses: Diving into the cold w/o retaining the warm

DiBartolomeo JR 1979
Exostoses of the external auditory canal
Ann Otol Rhinol Laryngol Suppl 88 (6 Pt 2 Suppl 61) :2-20.

Exostosis of the external ear canal is a disease unique to man. It has been
identified in prehistoric man, affecting the aborigines of the N.American
continent. Aural exostoses are typically firm, sessile, multi-nodular bony
masses which arise from the tympanic ring of the bony portion of the
external auditory canal. These growths develop subsequent to prolonged
irritation of the canal. The large, primitive jaw of prehistoric man placed
great mechanical stress on the tympanic ring. Chronic aural suppuration seen
in the pre-antibiotic era was soon followed by exostoses. Today, prolonged
contact of the external ear canal with cold sea water is the most prevalent
cause (aquatic theory). As a result the disease is now essentially limited
to coastal regions. In this way we have seen exostoses appear in different
stages of the evolution of man as a result of mechanical, chemical and now
thermal irritation.

The author, DiBartolomeo JR, is an otolaryngologist in a coastal region.
In examining 11,000 patients during a 10-year period, 70 cases of
symptomatic exostoses of the external auditory canal were identified. The
incidence of exostoses was found to be 6.36 per 1000 patients examined for
otolaryngologic disease. It is a predominantly male disease. The development
of these "irritation nodules" is painless until the tenth year of aquatic
exposure to irritation, when symptoms of obstruction occur. The hearing loss
associated with exostoses is usually a conductive type, secondary to
occlusion of the canal by impacted cerumen or acute external otitis. The
results of studying the thermal characteristics of the body of water used
for such aquatic activities is presented.

DDeden (Thanks MV at AAT for noting article and VR info)
 
Last edited:
Do most of those fish live somewhat amphibiously, compared to pelagic ocean fish? If so, air conduction would be significant, as it is in frogs and seals. AFAIK most ocean pelagic fish have one inner bone connected to the inner ear, while mammals have three. (I'd guess sharks have none). Do you know for certain that these (catfish, loaches) fish while at depth have air-filled bladders connected to their ears? Can the bladders empty at depth, (or fill with water or oil) and then refill with air at the surface? It is also possible that their ears are functionally deaf at depth but they pick up (hydrosonic) vibrations via their lateral line and/or bones.
Most of those fish live in relatively shallow water (less than 10m) because most freshwater habitats are not very deep. The Carp and Tetras do not ever leave the water, but many of the Catfish and Loaches will leave the water in wet weather, in search of new ponds and rivers. Most species in these orders can breathe air, using their intestinal tract (Loaches, Corys, Plecos) or modified gill chamber (large Catfish).

More about the air bladder...
http://forums.deeperblue.net/627049-post70.html

I think there's a freshwater fish that squirts water up at flying insects, I would guess that fish has good air-conduction aural capabilities (ear-air-sac), but also good water-conduction aural capabilities.
It is the Archerfish, Toxotes sp. It hunts by sight, so it probably does not need to hear its prey.
[ame=http://en.wikipedia.org/wiki/Archerfish]Archerfish - Wikipedia, the free encyclopedia[/ame]

o0O0o0O0o0O0o `<8{(((>< o0O0o0O0o0O0o
Good one, I have been trying to make fish pictures too.:)
 
Most of those fish live in relatively shallow water (less than 10m) because most freshwater habitats are not very deep. The Carp and Tetras do not ever leave the water, but many of the Catfish and Loaches will leave the water in wet weather, in search of new ponds and rivers. Most species in these orders can breathe air, using their intestinal tract (Loaches, Corys, Plecos) or modified gill chamber (large Catfish).

More about the air bladder...
http://forums.deeperblue.net/627049-post70.html

It is the Archerfish, Toxotes sp. It hunts by sight, so it probably does not need to hear its prey.
Archerfish - Wikipedia, the free encyclopedia

Good one, I have been trying to make fish pictures too.:)

=d(@^@)b= <-- funky fish! :)

Ok, so if fish which use air-conduction hearing typically dwell within 10 m of the surface, then that fits with my expectation, that it is a surface adaptation advantageous to them, regarding predators and/or prey. Perhaps some deep dwelling fish also use air-hearing for special functions.

AFAICT, this does not conflict with what I was saying about archaic human seashore divers/backfloaters using water-conduction hearing during their dive-foraging cycles, when hearing the dive partner was more significant than hearing prey or predator.

Allowing sun-warmed, UV-sterilized blood-temperature surface saline into the external ear, middle ear & sinonasal cavities just before diving deep meant that cold water at depth would trigger the facial and trigeminal nerves on the face maximizing the MDR, (unlike a full face mask & hood), yet (presumably) avoid the accompanying ice cream headache typical of prolonged cold water immersion of the bare face and forehead. This kept the brain warm at depth (conserving oxygen and energy), while the blood from the extremities moved towards the body core and the rest of the body acclimatised to the chilly temperature. Upon resurfacing, backfloating allowed maximum solar absorption, and blood returned to the small blood vessels of the sunwarmed extremities.

DDeden
 
Last edited:
I put together a summary of sorts of some of the suggestions in this thread regarding deeper scooter free diving on another website, portions reproduced below. Any other ideas? That is aside from seeking out a genetic throwback from possible artesinal free diving foraging ancestors? Wouldn't be all that much fun anyway, they'd get to do all the diving.

- You don't want to be further down than you are able to ascend from without aid of the scooter. If something happens to it, you ditch the scooter and ascend. I've decided to rig a small pony bottle across the small of my back just in case. Might even use it for a safety stop at times.

- Some have said to be sure to ascend particularly slowly in the last 33 ft. and even to stop for a while there to off gas. One diver mentioned doing an O2 safety stop at the end of the day, could make an important difference.

- As always, hydrating thoroughly is advisable.

- Others have indicated some issues with very rapid ascent, faster than I could go with the VS scooter on the order of almost 10 ft. per second. I think the VS was moving at less than 1/3 that speed. Anyway, all that speed can lead to barotrauma and disorientation or vertigo due to middle ear issues. So, motoring at reduced speed on ascent seems to be prudent.

- Still others talked about lung and trachea squeeze at depth, perhaps a bit deeper than I was hitting on this series of dives. It was advised to increase diving depth slowly over weeks to try to allow the body to acclimate to the new stresses.

- Another warned of hitting the wreck while under power. You could easily knock yourself out going fast on a scooter. A helmet is a good idea to try to reduce impact damage along with slow operating speeds and careful vigilance to avoid slamming into stuff. It is pretty easy to hit things motoring around a wreck, so have a care.

- It doesn't appear to be a good idea to mix SCUBA diving with this sort of activity. We still don't know a lot about residual nitrogen from SCUBA diving and impacts of free diving on promoting DCS other that it sometimes does just that! Some advise treating free diving like flying, only do it once you have cleared out all residual nitrogen or 24 hours or more after your last SCUBA dive. Seems strict but DCS hits are no picnic and worse tend to reoccur even easier at the same locations.

- Have your buddy carefully examine you for signs of cyanosis upon surfacing and other unusual indications. If you start to feel odd, break, increase surface interval for recovery or call it a day as indicated.

There is more along with some photos related to the wreck dive that got me thinking about this at:
[ame=http://fksa.org/showthread.php?t=4490]Deeper Scooter Free Diving - Spiegel Grove - FKA Kiteboarding Forums[/ame]

Thanks for all the ideas and suggestions!

Rick
 
Last edited:
Just went out today for some shallow scooter free diving under 70 ft. closer to home off Boca Raton. I was hoping to do some of that gradual transitioning that Paul Kotik recommended. Unfortunately, the weather and current conditions deteriorated shifting the destination away from the planned wrecks. With fairly poor viz., about 30 ft. and raging supercells just inland it made for a fairly distracting session. Despite that it was still good for some evaluation.

It was the first time out with a functioning Sea Doo Explorer scooter. They are selling them pretty inexpensively currently, around $600. USD. I rigged a tee seat expecting it to be a bit faster than the VS scooter. It is still a low end consumer scooter but I was hoping it would perform reasonably well anyway. Still checking the quality out and am hoping for the best at this point. This model as three speed settings readily switchable by repeated trigger pulls and a reported 2 hour battery duration.

On descent I motored at full speed using one hand for the trigger and the other for equalizing making things easy. On ascent a few dives into it I experienced some slight vertigo similar to that described by Eric. I was a little congested initially and suspect differential equalization was at the root of things as he indicated from ear pops and squeaks on ascent and not descent per normal form. So, I backed off to the middle speed setting for ascents or even the low setting at times. Later I trimmed for a bit more positive bouyancy and would turn the scooter off and gently ascend close to the speed of slow bubbles in the upper 20 or so feet. This allowed a time to relax a bit. I need to experiment with the tee seat bridling some more to improve performance.

The speed of the unit was good on the high setting but still just over 3 mph per the spec sheet. Hope to get it out again soon in good viz. and minimal current for more evaluation and practice.

Rick
 
Last edited:
Just an update, I wanted to pass along some hardware experiences for divers thinking about moving into scooter free diving. I have had a Seadoo VS scooter for several years. It wasn't a powerhouse but it was inexpensive, light and functioned reasonably well.

Wanting to move up a bit I recently bought a Seadoo Explorer just before a quick trip out of town. I wasn't able to take it into the water before flight time so I discovered the problem after I arrived. The drive shaft from the motor apparently has an internal linkage that decoupled within the motor housing. I shipped that one back to the retailer, who was very helpful by the way. He offered me a full refund and I figured, well lets try again. I asked that another unit be shipped out.

The second unit collected about 1/2 inch of water in the battery compartment after a few free dives under 70 ft. the first time out. All the seals were in place, lubed and free of grit, hairs, etc. that might impair sealing. Hoping it might have been a fluke, I took it out the next day for a beach free dive no deeper than 15 ft.. This time I collected water droplets within the battery compartment. Also, I noticed gas escaping from the "sealed" motor housing at the base of the battery compartment. Looking online, I understand some other Explorer units have had leakage problems. I've spoken to Body Glove the importer who was sympathetic and have attempted to speak with their repair center about time frames and likely outcomes several times without getting a call back. So, I will throw the towel in and ship the second scooter back to the retailer for a refund and start over. I understand another fairly large retailer took them off the floor and shipped them back recently.

Bad luck, to be sure but at the same time apparently fairly poor QA/QC at the factory. I am now looking around for another scooter to buy and may bite the bullet and get something more expensive again. Anyway, for what it is worth, buyer beware. You may fair better, then again, maybe not.

Rick
 
Last edited:
ricki,

thanks for the updates from the wide-world of scooter freediving.

sorry to hear of your latest mechanical malfuntion. keep us posted on your continued progress.

cheers,
sean
 
DeeperBlue.com - The Worlds Largest Community Dedicated To Freediving, Scuba Diving and Spearfishing

ABOUT US

ISSN 1469-865X | Copyright © 1996 - 2024 deeperblue.net limited.

DeeperBlue.com is the World's Largest Community dedicated to Freediving, Scuba Diving, Ocean Advocacy and Diving Travel.

We've been dedicated to bringing you the freshest news, features and discussions from around the underwater world since 1996.

ADVERT