How do you judge VIZ

[LakeCountyDiver]

This is a silly question but I have nothing to do today. Going diving tomorrow and Thursday thou.

How do you judge VIZ? If you put 10ft was it a clear 10ft or only a clear 4ft then after 10ft you lost images. Do you judge it by how far you can see hand signals. Just do you plain guess.

 

[CardShark]

Normally, it's the distance at which you can no longer see an object. Sometimes a Secchi disc is used : What is the SECCHI disk?
After practice, though, I think many divers guesstimate by comparing known reference lengths.
A great way to sharpen your perception while practicing skills is to run a line out from the wreck with your reel / spool, especially it's knotted at specific distances. You can determine the vis in 4 minutes in Florida ( or 1/2 minute in Jersey ).

 

[ScubaFeenD]

The dive log software I use only has general categories: bad, average, good. I think that those categories are actually far more useful than guesstimation of some distance. If i thought "wow, this is amazing vis for this location," then i put good. IF i think, "holy god I couldn't see anything here, " then I put bad. If it was pretty much the same as usual then I just put average. I am so bad at determining linear distance that the whole number game and making judgements based on where contrast and definition exist at a given distance would be useless for me.

 

[GFuterfas]

Great thread! I was wondering this recently when I got back to the boat and the DM asked 'How was the vis?' I said 'About 20 feet', which I thought was pretty good for SoCal, but as I thought about it I realized I was just guessing and could be way off. Anyway, I'm a fairly new diver and estimating distances underwater is very different than on land (which I'm fairly good at).

I like the reel idea, but not sure if my wife will care to help me run a line so I can more accurately determine the visibility.

 

[fishguy]

Great thread.

I'm one that tends not to try not to estimate distance in ft or m. I like to use terms that are easier for my own reference.

Crud...not bad...wow

 

[fjpatrum]

I answered "how far I can see hand signals" but that's really only true in "low viz" situations. In blue water, viz is just how far I can see things, period. If I'm at 70 feet and I can see the boat (and know it's a boat) for example, then viz is 70+ feet. If I'm 20 feet away and I can see my buddy is there but can't see what he's doing specifically, viz is <20 feet.

 

[Lead_carrier]

The only time I'm concerned with viz is if I have students in the water. Then it must be in the fair range at worse. I do like a handful of others, Bad, fair, good, etc. Of course if you're doing the Cooper River that's a different story. Good there would be horrible other places.

 

[fisheater]

In Reef Check California, we measure and record the vis by having one dive buddy swim down the transect line (a 30m/100' measuring tape) holding up a fingers. When the buddy at the end of the line can no longer count the number of fingers, he signals and the other buddy notes the distance on the line.

Or, like we do on our non-survey dives, you can guess.

 

[Dhboner]

In descending order:

Amazing, decent, crap...post-open water students

 

[CGADivebum]

I catagorize viz as great, good, bad, or muck. I don't usually record distance in feet for my logbooks. Too hard to figure out unless I have a known reference like a wreck. Besides, distance is relative. 10 feet in Hawaii, is terrible, 10 in the Chesepeake Bay is awsome!