Where was the best visibility you ever encountered?
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KidK9
Contributor
The one time I was supposed to dive at Grand Cayman, I got blown out (was on a cruise). I didnt realize that the water was that clear there.
rockjock3:
I'm not sure I've ever read anything "scientifically" satisfying about this subject. However, I think there is a passionate topic here that has been debated before on the board. In my diving circles we believe horizontal vis typically to be at least 33% "worse" than vertical visibility - but this is only based on personal observations. I've heard divers on this board argue hard that vertical visibility can be 2x greater than horizontal vis and they stand by that statement. Clearly there is some science behind this perception and experience ... the sunlight is bouncing off of surfaces and sending that light back into our eyes. A sandy bottom or reef makes a nice surface to reflect light back to a person looking over the side of a boat, whereas a diver in that same water looking horizontal doesn't really have a reflective reference. Then there is particulate in the water which reduces vis by interferring with the penetration and thus distance that the light can travel, but particulate may reflect in different manners. Then you have a situation like an algae bloom which prevents any view of the underwater world from the surface but as Uncle Pug once so eloquently put it - once you decend below this, it's like breaking through the clouds, the visibility just opens up! Yet what is perceived then as visibility would not be possible unless a certain amount of light had already penetrated the clouds in order to get down here. Also once in the water you have the 25% magnification distortion. And in all the known materials, on more than one occasion SB has debated the comment made in one PADI publication about certain conditions related to visibility underwater may actually cause objects to seem further away rather than magnified ... ahem, no comment. Clearly perception of horizontal vis vs. vertical vis is based on environment, weather conditions, water conditions and other factors. I read a few years ago that our brains detect objects in vertical vs horizontal fashion differently as well. For example, when viewing a new moon (harvest moon for example) cresting on the horizon it seems magnified. For years folks would say this is an Earth's atmospheric magnification, yet that same moon high in the sky on that same night seemed vastly smaller by comparison. Then I read some scientific research into the way our brains percieve it. The experiement said next time you see one of these "rediculously" magnified moons, find an open flat area lay on your back with the top of your head pointing toward the rising moon on the horizon, then tilt your head back to look "up" at this moon (simulating what it would be like to see the moon high overhead, instead of on the horizon). Well guess what I did it, and you know what they are right the brain seems to translate things differently depending on the position of your head. I thought I'd be duped it seemed so silly, till I tried it!
I can understand that bright light striking the waves makes it easier to see them but if you're 30 metres under the water and you can clearly see the waves you're still looking through 30 metres of water....and you're still looking at an object 30 metres away.....assuming no thermoclines, haloclines, algae blooms etc.
Personally, I think that vertical viz is a adequate measure of vizibility. Even if you can only see 80% of the distance horizontally because of reduced light, using the measurement of seeing clearly defined waves on the surface is consistent, accurate, and easy to apply. Maybe not in every possible situation, but for a large number of dives it is.
R..
Personally, I think that vertical viz is a adequate measure of vizibility. Even if you can only see 80% of the distance horizontally because of reduced light, using the measurement of seeing clearly defined waves on the surface is consistent, accurate, and easy to apply. Maybe not in every possible situation, but for a large number of dives it is.
R..
ScubaCo:
That's gotta be a new reverse record
Anyhow:
One of the best places in the world viz-wise is alledgedly on Thingvellir, Iceland. Book says there's a viz of up to a 150 metres - and that's metres, not feet.
"Silfra is a lava ravine in Þingvellir, Parliament Plains, caused by the drift of the two continental plates Eurasia and America. The ravine constantly receives new groundwater that originates from the glaciers and has been filtrated through the lava for 10 – 20 years. The filtration results in crystal clear water offering extraordinary visibility."
It's drysuit stuff and horribly expensive and I'm definately going
Get a load of these ...
KOMPRESSOR
Contributor
Norway, Hitra i February 2005. Had pretty good wiz. About 40 meters (130ft). During a night dive with a full moon, the moon lit up the ocean floor at 26 meters (85ft). We turned off the lights and could still see each others, and the surrounding rocks. -And the moon looked like a strong HID-light in the distance...
Same place, same day, daytime. Not the same great viz as during the night dive, but good enough!
Same place, same day, daytime. Not the same great viz as during the night dive, but good enough!
KOMPRESSOR
Contributor
Diver0001:Iceland is on my to-do list too!
I heard you can take a ferry from Denmark. Is that true? It would be nice to go with my own car....camping stuff....portable compressor......
R..
I don't know about the ferry. There are boats going from the west coast of Norway I've heard, and most likely from Denmark too.
But from what I've heard you can't just drive up to Tingvellir and dive on your own. I think you have to go organized, and pay the fees... And it is expensive! There's hardly any life there but a very few trouts. This is not to try to take your wish to go there, because it's awsome I've heard. Many divers from Norway visit every year. Just notice the water is freezing all year round... (And spoken by a Norwegian too!
)
captain
Contributor
250' horizontal, Louisiana gulf coast, Shell Oil platform 50 miles offshore on the edge of Mississippi Canyon.
Depending on conditions vertical visibility can be better, worse or the same as horizontal visibility. When there is a difference, it can be a small difference or a large one.
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