Interesting situations

I've been experiencing a couple of interesting situations recently and am hoping someone might be able to explain them to me. I've noticed both of them over the past two times I've been out, just as recently as this afternoon.

1. I dive down and am finning along the bottom of the pond, 15-18 feet down. Everything is fine at first, couldn't be better. All of a sudden about half way through the dive I notice what seems like my vision is closing in one me. It gets to the point to where it seems like the width of my vision has been reduce down to 2-3 inches, everything else seems to turn white all the rest of the way around.

I am wearing regular swim goggles. I haven't had this experience except for the past two times I've been out. Both of the two most recent times has been after the sun has went behind the trees, leaving the water darker. The goggles aren't leaking and when I come up and surface everything is fine. When I go back down it happens all over again the same way.

It is definitely got to be rather annoying.

The only thing that I have changed is to put on a swim cap, and today I even put on a extra layer under the swim cap. All this is under the regular, 'loose fitting' hood.

2. This one is definitely strange, but not problematic like the one above. I'm on a dive, I'm finning along slowly coming up and in a horizontal, not vertical fashion. I get to a point where I think I'm pretty much at the surface to only find out that I still have 3 feet or so before I'm actually at the surface. This happens on every dive. Fortunately, I have been practicing the montra of keeping the snorkel out of my mouth the entire time I'm under. I don't try to put it back in before I surface thankfully, otherwise I would probably have to yank it out or choke on water.

Why do I get this strange miscue of where the surface is. I haven't ever checked to see where I'm weighted at, my vocabulary is failing me right now.

Thanks,
Ryan

turtle said:

mate, with all due respect and goodwill, your 'situations' sound more like very close calls!

You don't mention anyone else - do you dive with someone at least?
Fred

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No, I dive by myself as no one else in the area does any diving.

I wouldn't call them close calls by any means. I never press it on any dives. I've never had contraction/urge to breath on any dive, I don't stay down long enough for it to happen, 45 seconds max on any dive most of time somewhere between 30-45 seconds.

I have changed one thing, other than the time of day, and that was putting on the swim cap. I've wondered if that has something to do with it. I'm going to have to try it tomorrow with the sun higher in the sky and see if that makes a difference. It does seems like when I invert myself, to come up on my back that I don't notice the problem. It's only when I have my stomach facing the bottom that I notice the vision closing in, as I think more about the dives from today. It's like I have white vertical walls inside the goggles that are separated by 2-3 inches. It's instant, it goes from not being there to being there instantly.

As for the second problem, I never thought about the change in light as I get closer to the surface possibly causing it. I'm going to have to pay attention to that tomorrow. I would really like to figure out why it is occuring. Is this something you would notice when you are at bouyancy????? It does seem like there is a change in the way I feel as I get faked out. Kinda part of the reason why I'm wondering if it could be that I have hit the bouyancy point and that might be what is causing the strange sensation. Figuring again, that you are horizontal in the water finning up slowly versus coming up vertical fast.

turtle said:

Your peripheral vision packing in is a precursor to a b/o or LMC, and is caused by low 02 if i remember. So, basically, it's a *bad thing* :rcard . I can't think of any reason you should be misjudging the surface apart from thermoclines or changes in light or something, but in any case it's definitely not good if your judgement is impaired at the end of a dive, no matter how deep.

Be careful ;-)

Fred

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Hence why I'm glad tylerz mentioned in another thread about coming up on your back, and why I also spit the snorkel out as I start down and don't put it back in. I remove as many obstacles as I possibly can.

Ryan

One problem figured out and the other is pretty close to coming up solved.

The eye problem, not from diving with goggles. I have been diving with goggles all along and in the same location, and to the same depth. Hence why I keep myself limited in how far down I can go, because of diving with the goggles.

The problem is a combination of time of day and cloudy water. I've pretty much been diving at the same time each day, but with the days getting shorter and shorter, in the northern hemisphere, it has made it so the sun is behind the trees/hills and isn't casting it's rays down on the water. The water, 6-8 foot visibility max. I would say it's probably less than that quite possibly. I know when I look down from the surface it's like I'm looking into a dark abyss. It used to be a light abyss thanks to sun.

Today, first dive, I'm down on the bottom and everything seems fine, then as I start to rise and get to the point where I can't see the bottom anymore I notice the vision closing in again. I immediately think and stick out my hand in front of my face, I can see the hand just fine and jimdandy. I realize by looking around that I can't see anything around me at all because of the lack of sun reflecting off of particles in the water and being too far up off the bottom. The answer to that problem was quickly solved, dive sooner in the day or expect the condition to continue, better yet get in clearer water.

Problem two, this one is still eluding me a little but I think I might be starting to figure it out. One question answered may very well solve this one as well. Here goes the question:

Coming up from a dive to only around 18 feet max, slowly, in a prone position you reach 2-3 feet below the surface, would a person normally notice a pressure change? This assuming no real notice of pressure change at any time until that point. Possibly to the degree where the pressure change might be enough to make the person think that they have reached the surface.

Yeah, yeah, yeah, the question does sound really strange doesn't it. This afternoon I was noticing it again and this time I was really paying attention trying to see if I could come up with a way to describe it better. It feels almost like a 'dramatic' pressure change is what I'm noticing that makes it feel like I have surfaced when I'm still 2-3 feet under. I wouldn't say it has anything to do with a change in lighting. I know it definitely has nothing to do with bouyancy, I tested that and ruled it out quite early on. It did seem though like I was noticing a pressure change that made it seem like I was back on the surface again. Would something like this happen 2-3 feet down when coming up from a dive/shallow water dive.

Thanks,
Ryan

Thanks for confirming my thoughts. It does help make sense why its so important to pre-equalize and why pre-equalizing helps out so much.

Ryan