Defining visibility

[formernuke]

If I can see my fins then the vis is 6-7 feet. If I can't see my fins then I just I head for the pub where I can clearly see my drink.

Don't come up here, you would never leave the pub.

I judge VIS on when I would no longer be able to see my buddy.

 

[Chavodel8en]

I was told - and I think it makes practical sense for most recreational dives - that its how far you can make out the presence of another diver (presumably your buddy).

So basically, I've always defined it by the lost buddy factor. This definition makes sense in California, where 20 ft viz is good diving, but 10 ft viz can make keeping your buddy a pain.

The pic OP posted looks like much better than 30 ft viz to me but I might be wrong.

 

[Eric Sedletzky]

I was told - and I think it makes practical sense for most recreational dives - that its how far you can make out the presence of another diver (presumably your buddy).

So basically, I've always defined it by the lost buddy factor. This definition makes sense in California, where 20 ft viz is good diving, but 10 ft viz can make keeping your buddy a pain.

The pic OP posted looks like much better than 30 ft viz to me but I might be wrong.

This is why I solo dive.
Chasing my buddy around to keep him in view, or looking to the side and he’s there, two seconds later I look again and he’s gone. Then spend half the dive searching around in circles looking for him because it’s suppose to be a “buddy dive”.
If it was looking for one minute and surface I’d be up 50 times to regroup. Low vis and buddy diving makes the dive just about staying with the buddy and not much else. Put a leash on him so he doesn’t sprint off like a feral cat!
So, at least with solo diving vis doesn’t matter as much to me as long as I can see the end of my spear gun, I’m happy. I don’t have to keep track of someone and vice versa.
If I shoot a nice ling and/or get a limit of scallops it makes me real happy!

 

[Bigbella]

Is there an actual technical definition of visibility?

There is some obvious "guesstimation" involved while sport diving; but it is often taken as a measurement from the surface, down, to a known depth.

One of my first gigs out of college, was measuring the eutrophication (the degree of algal growth or, primarily, overgrowth) of some freshwater lakes and estuaries; and we'd use a 30 cm Secchi Disc (seen below), to determine the level of turbidity. It is lowered from a boat, usually on a calibrated rope until when or if the stark black and white pattern is no longer visible, later using an extinction coefficient (for this purpose, the "ease" of light penetration in a liquid medium) to determine clarity. A high score reflected good visibility; a lower number, its opposite.

A friend found a 15 cm Secchi sticker somewhere, that he mounted to one of his tanks; and while he was diving to a reef off of Jupiter, Florida, of known depth, I could just see it from the surface -- a good indicator of about twenty-five meters of visibility . . .

 

[TMHeimer]

I read somewhere in the PADI materials that some divers say it's the distance you can make out another diver. Does that mean "see" another diver? Or that you see a blur that MAY be a diver? Anyway, that's what I try to imagine (I dive solo) for my log book. Sometimes I can see a rock ahead of me and make believe it's a diver.

 

[tomfcrist]

I always tell folks that the Vis is as far as the eye can see. Some get it, some don’t.

In reality I see 4 different vis levels…not how many feet. Unlimited(100+), pretty good(60-100), meh(15-60), and Hellen Keller.

 

[Searcaigh]

I haven't, but it would be s good exercise. As viz varies by depth, it would be interesting to measure viz at the surface versus 20 feet vertically and horizontally at the same depths

Where I regularly dive off the east coast of UAE we generally go through a layer of several meters of low vis.

On a normal 28-30m dive we can have low vis from 10-20m depth then it opens up from 20m where you can see the bottom, but when you get to the bottom the horizontal visibility may only be around 5m. It's a bit weird.

Sometimes we have great vis in the top 10m then it goes to sh!t all the way to the bottom with only 1-2m in any direction.

 

[CycleCat]

On a normal 28-30m dive we can have low vis from 10-20m depth then it opens up from 20m where you can see the bottom, but when you get to the bottom the horizontal visibility may only be around 5m. It's a bit weird.

I always assess vis on my dives once I reach my goal depth. Where I dive in the Sea of Cortez it's been pretty consistent from the surface to depth.

 

[arew+4]

I put it at the distance I could take reasonably sharp available light photo.

 

[vemura]

Dive buddy and/or instructor and I estimate and agree together, but after all, it's your log, with your feelings and thoughts on the experience.