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How to predict good visibility?

Fishstab

Member
Jun 16, 2020
28
14
8
32
South Somerset
What are some of the key indicators you look for to assess whether the visibility is likely to be good or not?

I went out yesterday evening and was predicting poor visibility as it had been the 2 days prior but it was really good. Would love to know what to look out for in terms of wind direction, speed, swells etc
 
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Mr. X

Forum Mentor
Staff member
Forum Mentor
Jul 14, 2005
7,647
1,458
418
Sunny Britain
My 2 cents: No rain for several days previously, as rain washes debris into the sea. Wind from the sea towards the shore of interest tends to stir things up, bad sign especially if the wind is moderate to strong. l associatr no wind or light wind from land concerned towards the sea with clearler conditions, especially if the wind is light. The above apply on dive day, and sometimes a day or two or three or four beforehand too.

The GB Windmap website can be useful. Click on the wind arrow nearest to your intended dive site.

I don't know if it's valid or sometimes valid but I often take sea surface chop as a bad sign. Not least because it often leads to sea sickness :sick: A flat mill pond like surface is usually a very good sign in my experience.
 
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DivingNomad

Member
Sep 21, 2015
48
18
23
USA
What are some of the key indicators you look for to assess whether the visibility is likely to be good or not?

I went out yesterday evening and was predicting poor visibility as it had been the 2 days prior but it was really good. Would love to know what to look out for in terms of wind direction, speed, swells etc
If it were very high seas with churned up bottom, it will take a day or two for the visibility to improve even if the sea is flat the day following the storm. This depends on the locations and prevailing water conditions. Generally, it is guess work that has a high probability of error and can't beat showing up at the site and checking visibility with your own eyes. To do it accurately means that you have to predict wind direction, speed, currents, tides, rain vs. sunshine, sea bottom topography, depth of dive site, bottom composition (sand vs. rock vs. plant life, etc.) and God knows what other local factors that all have to line up perfectly in the prediction of each one of them to make a gross prediction that includes all of the factors to predict again the visibility. If any single factor deviates from its predicted state, the sum of the predictions will fail making the visibility prediction wrong. At the end, you have to show up at the site you intend to dive and observe the visibility with your own eyes and decide if it is worth diving.

My opinion above is shaped by my several decades of primarily shore diving in the southern Mediterranean, NE USA (New England, NY and NJ) and other locations around the world.
 
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Mr. X

Forum Mentor
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Jul 14, 2005
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Sunny Britain
Good point about location. Some locations are "fussier" than others. Perhaps due to the type of bottom (sand, rock, weed, etc.) and sheltering factors, such as reefs, sand bars, headlands, spits, harbour walls, tombolo, etc.
 
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spoolin01

Well-Known Member
May 20, 2008
32
3
98
Bay Area, California
What are some of the key indicators you look for to assess whether the visibility is likely to be good or not?

I went out yesterday evening and was predicting poor visibility as it had been the 2 days prior but it was really good. Would love to know what to look out for in terms of wind direction, speed, swells etc
Ha ha if you figure this one out, let me know! Some places viz is correlated with the tide - better as the tide builds than as it recedes, but that won't work everywhere. River mouths or surface runoff is another obvious problem. Some places it's clearly affected by swell height stirring up stuff in the shallows. Around here in northern California, where the problem is mostly plankton I believe, there's no predicting it, aside from winter being generally better than summer.
 

zazuge

Member
Jun 30, 2018
47
7
23
38
ghardaia, Algeria
As said by other posters, Rain will make water muddy for several days
i remember one time i had only a week on the coast, and it rained the 1st day, it took 3-4days for water to start to clear up
also, if its close to an estuary, it's gonna be bad after a rain
gulfs and the like will stay bad longer than caps, caps usually clean fast because of sea currents
swells also count, specially when its sandy shore (in case you're doing shore entries)
 
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