How is “visibility” defined?

[ghostdiver1957]

Low vis is extremely easy to figure out... Jump in the water and look down. If you're six feet tall and have on fins (about 18 inches) and can barely see the fin tips, the vis is about 7-8 feet... can only see half your body... vis is 3-4 feet.

Use this same concept to establish vis of greater distance. Determine your distance with body length and fin kicks. Its not an exact science, but you can definately estimate within 10 feet what the vis is. Use your body and or your buddy for measuring distance. Once you master it, you can safely tell someone vis was 30-40 feet 70-80 feet etc...

 

[wardric]

Diving mostly in environnements with thermocline, I have to define viz at each layer cause there is a huge difference in most cases.

As for the way I do it, it's subjective like: none, crappy, medium, good, very good and excellent, none being like if you dont see your hand stuck on your mask. It's a personnal and subjective information but still a good indication. Of course, if I spend a week in the caribeen and I come back to my cold lakes, a usually very good viz could seem like a crappy viz...

When I dive, I dont have time to lose trying to mesure with a tape the distance to where I can see.:05:

 

[NauticalbutNice]

If you can only see as far as your hand in front of your face, you have bad viz.

If you can only see as far as your buddy next to you, you have ok viz.

If you can see as far as the wreck/reef, you have good viz.

Simple?

Nauticalbutnice :fruit:

 

[drew52]

If you can only see as far as your hand in front of your face, you have bad viz.

If you can only see as far as your buddy next to you, you have ok viz.

If you can see as far as the wreck/reef, you have good viz.

Simple?

Nauticalbutnice :fruit:

Good answer no need to get caught up in the scientific approach; either the viz is good or its not. If its pitch black (during the day) at 30m the viz is bad, if I can't see my buddy with his torch off(during the day) its bad.

If its not bad then it must be good? I'm also with the simple approach.

 

[String]

Not really applicable as "good" for one site can be "bad" for a neighbouring site and so on. Different people also have different ideas of "good" and "bad" visibility.

Some people class 15ft as good whereas others class that as so bad its undivable. Having a scale to compare makes sense.

 

[NauticalbutNice]

Exactly! Good/OK/Bad are the only answers you'll get from me.

I'm a simple diver (in more ways than one )

If it's someone who doesn't know the sites that is asking I'll elaborate with specifics (5/10/136m).

If not, you'll get "Good...".

 

[Diver Dennis]

Very interesting Rick. First time I heard of these.

 

[wardric]

Not really applicable as "good" for one site can be "bad" for a neighbouring site and so on. Different people also have different ideas of "good" and "bad" visibility.

Some people class 15ft as good whereas others class that as so bad its undivable. Having a scale to compare makes sense.

I agree, that's why the good/bad system is, and must remain, a personal system for each diver's use only. For that use, it is acceptable, but of course for information to other divers, another system like distance must be used, although even distances are not evaluated equally by different persons.

 

[Ishie]

I try to guesstimate vis. Once it's over 30+, my official estimate is "outstanding", whether that over is 35' or 250'.

It's funny. When people were talking about the Philippines, who've done most of their diving in the Caribbean, some were like "well, the water will only be 77-80 degrees, and while the vis can be spectacular, it can also be only 40 or 50', and I'm thinking "are you kidding???"

In Monterey, I'm more likely to determine the quality of the vis by what things look like, versus how far I can actually see. I've dived very gloomy looking 20' vis, which was nice, of course, but kind of dreary, versus dives with 10' horizontal vis, but which were light, but had a lot of light particulate in the water that hazed stuff out, that were "cheerier".

So far worst vis was about 6-8" during an advanced dive. Could read gauges if right near mask, but instructor had to touch my shoulder for me to be aware he was there!

 

[SeanQ]

Good answer no need to get caught up in the scientific approach; either the viz is good or its not. If its pitch black (during the day) at 30m the viz is bad, if I can't see my buddy with his torch off(during the day) its bad.

If its not bad then it must be good? I'm also with the simple approach.

I've been at 30m in the Saanich Inlet before and had great visibility in the dark. The top 10m is likely algae soup though. It's almost like a night dive at lunch time. Too bad the nocturnal critters don't always feel the same way.