How is “visibility” defined?

[UB]

I recently did a dive with what I defined as 2-3ft “visibility”. I defined this as - I could rather clearly make out objects that were up to 2-3ft in front of me, everything beyond that distance was blurry (but I could make out some "shapes" that were ~6ft away). Is this the correct definition?

Thanks

 

[MXGratefulDiver]

I think it's pretty subjective. My definition is that if I can see it, it's visible ... even if I can just barely make it out. So by your description above, I would call that 6-foot visibility.

... Bob (Grateful Diver)

 

[Dive-aholic]

A topic with a vast difference of opinion as evidenced by previous threads on the subject. There are several acceptable definitions. It's all very subjective. My gauge - I estimate the distance to objects which I can make out what they are, blurry or not. The only time I vary from this is in black water. I may know my gauge is my gauge when it's 6 inches away, but if I can't read it when I place it against my mask, it's zero viz.

 

[Rick Murchison]

Use a Secchi disk.
Rick

 

[WetDawg]

Very subjective unless you carry a secchi disk with you

http://www.mlswa.org/secchi.htm

 

[spectrum]

I reference something else like:

The end of my glove was cloudy
I could spot divers and structures at 15'
My enjoyable viewing as 5'

Now I need to research Secchi disk.

Pete

 

[spectrum]

Stick a secchi disk on the bottom of your buddys cylinder?

 

[CDFDiveMaster]

What's viz got to do with it....who needs viz. Feeeel your way. That sudden surprise is the best, just make sure your have enough in you to deal with it. Just kidding! That's about right, I actually look from the boat over and if I can see the bottom, I look at the depth sounder on the boat and there you go wa la! Viz. Peace

 

[String]

Visibility tends to be subjective.

The proper way of doing it is with a white/black disc lowered from a boat vertically into the water until such point where you can no longer distinguish the different shaded areas.

You tend to find divers are better at guessing visibility in the range of what they normally dive in. Take a warm water tropical diver and put them in low visibility and you often find they underestimate the vis. The reverse is also true, take someone used to diving in 3ft water and put them in 100ft vis and they'll just make a wild guess.

I tend to define visibility as when i can no longer distinguish the outline of an object. In a way lower visibility makes it easier. I know a standard buddy with fins on is roughly 2 meters long. If i can see their fin tips and their head i know the vis is over 2 meters. I tend to use "buddy lengths" to guess further. Obviously this breaks down abroad in better conditions but i generally find it works fairly well here. Quite often we get different people all coming out of the water quoting the same estimated visibility figures.

If i can see the bottom off the boat it means the boat has run aground....and even then normally you cant see it

 

[WetDawg]

Remember that horizontal viz and vertical viz can sometimes differ greatly at various locations.

Typically this is influenced by depth and ambient light.