Maybe dumb ? about visibility

[MauiScubaSteve]

From the link in Mike Boswell's post above;

As a general guideline, if you divide the vertical visibility by half, you’ll come up with horizontal visibility. (You can usually see further looking up, since you are looking toward an area of greater illumination.) In other words, if vertical visibility is approximately 60 feet, horizontal visibility is probably somewhere around 30 feet/9 meters

I was led to believe horizontal visibility is what we talk about as divers. If you make many good vis wreck dives on wrecks you know the length of, you can learn how to make better guesses, even when you are not diving a wreck.

I'm of the opinion the vast majority of warm water divers over estimate the vis, especially when marketing/bragging in any way, shape or form.

 

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over[/B] estimate the vis, especially when marketing/bragging in any way, shape or form.

Ive also heard some people under-state the vis to get some sort of macho kick out of it. "The vis was 6 inches!" when it was 2-3m in reality etc.

 

[k ellis]

Well if you jump off the boat and can see the bottom then ask how deep it is before you dive. If they say its 100 feet deep then its a least 100 foot visibility I have dove in places where my hand was 6 inches in front of me and could not see it. In molokini we were about 250 feet away from the wall and looked under the water and could see the shore line from below clear as day so I knew it was well over 200 feet vis.

 

[spectrum]

Ok, this maybe is a really dumb question but oh well.

When your diving how can you tell the visibility? I understand that its as far as you can see. But how do you estimate that in feet (or whatever unit of measure). I have terrible sense of distance so I'm not sure short of taking out my tape measure how far it is.

I guess what I'm asking is do you all just estimate and say "oh that looks about 10 feet away" or is there some good way to judge the visibility that I'm not aware of?

My yardstick is diver lengths which with fins is about 7 feet. From there I can multiply and adjust.

I also us a "local scale" reference. There's no sense in comparing against a pristine spring or perfect day day in the tropics. A 5 on a local scale of 10 is average and I estimate from there.

There are more technical metrics but for communication and logging this seems to work.

Pete

 

[Teller]

Since I have a depth gauge with me, I tend to use it to get an idea of depth if the water's deeper than the visibility distance.

If I'm on a wreck that I know is at 100' and while I'm surfacing, the details of the wreck get hazy it's nearly lost in the blue when I'm at 30' then I know the visibility is around 70'.

If I'm in really shallow water and people on the boat can easily see the reef and the sand, that's not going to help, but having seen what visibility of 70' looks like on something like the above-mentioned wreck, you can compare the visibility on the reef and get an idea about how far.

I also sometimes imagine easy-to-visualize objects of known size for reference. "If our 65' boat were to sink, would I be able to see both ends?" as an example...

This method is not very accurate due to the fact that the sunlight will make the vertical visabily better. There is a difference between horizontal visability and vertical visability. This method would work if you were at one end of the wreck and you knew the distance to the other end of the wreck.

 

[Hatul]

I look at the vis scale analogous to when we ask someone in pain to rank their pain on a scale from 1-10. The number is a subjective assessment of how we feel about the viz we experienced on the dive.

Adam

 

[D_B]

Diver length is a good yardstick


heh, a once heard 1 to 10 pain scale ...
1 is a flea biting an elephants butt
10 is an elephant biting a fleas butt

:bounce3:

 

[MauiScubaSteve]

I'm of the opinion the vast majority of warm water divers over estimate the vis, especially when marketing/bragging in any way, shape or form.

In molokini we were about 250 feet away from the wall and looked under the water and could see the shore line from below clear as day so I knew it was well over 200 feet vis.

You were just trying to more than make my point, right?

 

[k ellis]

You were just trying to more than make my point, right?

LOL I wasnt doing neither. The majority of my dives are extremely low vis (Less then 10 feet) and less then warm water. Usually around upper 60s to lower 70s with nothing to Market. But hey its all good

 

[MauiScubaSteve]

with nothing to Market. But hey its all good

Well, there was that other option! :shocked2: