Determining Visibility

[SparticleBrane]

Ken, remember that the visibility in a pool is determined by how good the filtration system is and how many people have recently been in the pool.
If the pool has been closed overnight with no one in it and it was filtered the whole time, chances are the vis is spectacular. As soon as people get in and start splashing around, now you have all sorts of great stuff in the water--bodily oils, skin flakes, etc, plus all the splashing puts tiny 'micro-bubbles' in the water. If you hop in after a swim-team practice you'll know what I'm talking about, the water looks positively cloudy from all the kicking.

In the pools that I frequent, I've seem huge changes in visibility from day to day. On eay I can see clearly from one side to the other in a 50m olympic size pool. Other days I've had issues making out the other side. On the worst of days I have issues seeing the other side, the short way (25m instead of 50m).

As to determing vis, I usually just estimate based on my surroundings. I try to estimate it based on where people or objects start to become lost in the gloom.

 

[drbill]

As a videographer, I define visibility in a slightly different way... it is the distance at which I begin to lose clarity in a recorded image. Therefore my estimates tend to be on the low end, but I usually state how I judge it if a non-imaging diver asks. Another way I define visibility is the greatestest distance I can clearly identify a great white shark approaching me!

 

[jeckyll]

You people have too much time on your hands if you are worried about hot to figure out if the viz is 75 or 100 feet.

We have: Good, OK and "I can't see my fins"

 

[mikerault]

Not if you are doing wreck photography, the diff between 75 and 100 foot viz can make or break a shot...

 

[ClayJar]

On my log pages, I have a viz scale from 0 to 100 feet. I have very few marks toward the high end of the scale, but a few times (in springs), I've just drawn an arrow pointing off the high end of the scale. (In the lower cavern of Morrison Spring, visibility is rock-limited. Perhaps I should add a check box for "all the way".)

Anyway, I don't really bother much with quantitative visibility when it comes to good conditions. I would be content with a scale that went something like:

• Can't see my gauge against my mask.
• *Can* see my gauge against my mask.
• Hand's breadth.
• Elbow.
• Arm's length.
• Knee.
• Ankle.
• Fin.
• Whole buddy.
• Stuff.
• Where I am.
• Whole wreck.
• Wow.
• You've gotta be kidding.
• Tropical vacation.
• Good as air.
• Good as space.
• Omniscience.

I usually dive somewhere between "fin" and "whole wreck", but I've had periods of "hand's breadth" or below. In the springs, I've made it all the way to about "tropical vacation" and a half, just shy of "good as air".

 

[J.R.]

I would be content with a scale that went something like:

• Can't see my gauge against my mask.
• *Can* see my gauge against my mask.
• Hand's breadth.
• Elbow.
• Arm's length.
• Knee.
• Ankle.
• Fin.
• Whole buddy.
• Stuff.
• Where I am.
• Whole wreck.
• Wow.
• You've gotta be kidding.
• Tropical vacation.
• Good as air.
• Good as space.
• Omniscience.

I usually dive somewhere between "fin" and "whole wreck", but I've had periods of "hand's breadth" or below. In the springs, I've made it all the way to about "tropical vacation" and a half, just shy of "good as air".

WORKS FOR ME!!! Gonna' spend some time on the ol' computer in the next day or two and come up with a personal log sheet that incorporates this (... or something darned close)... I love it...

 

[diver 85]

It's really a guess sometimes(even in the Carribean) but the 2 times I KNOW it was approaching 200 ft was (1) while diving the Ore Verde in Grand Cayman( 185' feet long)in the early 90's we could easily see divers @ the other end of it & (2) in '00 while diving the El Aguila in Roatan, we could look up & read AKR on the side of our dive boat from the bottom(110')- in fact my son was filming that dive for AKR(we have it on the tape) & remarked that was probably the best viz he had seen on Roatan in almost 3 yrs there then......

 

[The Kraken]

Clay Jar,

I LOVE your visibility scale !!!!
Best one I've ever seen!

the K

 

[fisherdvm]

Do they make an underwater range finder - I mean, kinda like a depth sounder device. I know that I have a scope that find range fairly accurately on land... How would a device work underwater, I wouldn't know.

I think the land device uses infrared or somekind of waveform to calculate distance, right??

 

[kf6alc]

One of our DM's in Belize (and awesome bartender, too) gave us a sort of 'rule of thumb'. As you descend, note the depth when you just can't make out the surface, then subtract 10'. As good as any guesstimate I know, but as stated before, this is probably only useful in clearer water. Here in Monterey, it's fairly easy to guess 8-10'.