Underwater visibility, how do I get accurate information.

Hi Skippy

I live 200 meters from an underwater marine park on the East coast of Tasmania. I'm also a keen diver and friends with the owner of the local diving centre.

My impression (guess) is that the visibility ranges from 5 meters to 50 meters underwater BUT at what depth? It can be poor vis' down to 10 meters deep and get better towards 40 meters. Your camera would not really give an overall impression. I'd thought of mounting it at the bottom looking up but that always gives a false reading. Vertical is always better than horizontal.

Vis is also weather dependent. If we get a Nor-Easterly we are buggered but anything with West in it and we are good!

Sorry to not have a definitive answer!

Oh! and to answer the second bit:- she won't miss it until she needs it. The missing button might be a clue but she will get really pissed when the salt water starts dripping out!

I would think that they would have device to do what you ask. Say a box with a light beam and intensity sensor. That could transmit a reading to shore and be place at any depth.

I would go for the divers perceptions, you would have a broader range of views over a larger area of water so could average out results.

A camera in one spot would only be relevant to that spot and moving it to another location on another day would not reference to the first location etc etc.

Have the divers put some markers { rocks painted different colors } in as many locations as you can handle and do a vis site marks out of ten and hope they are not color blind.Then treat them to drinks at your local.

To do it "scientifically" you may want to check out this site that I googled up on a DIY Turbidity meter.

http://instruct1.cit.cornell.edu/Courses/ee476/FinalProjects/s2005/jsa25_jyh25/TurbidityMeter.htm

May be a set up with a pump and glass tube for a testing chamber would permit a continuous sampling scheme. Or perhaps an instrument rental company could set you up with a meter and dataloger to run a one time test.

You will find what you need at:

http://www.oceanoptics.com/

Incredible research done on multitudes of oceo-graphic topics , and more equipment than you could shake a ... ummm ... starfish at!

"If they don't have it, you don't need it!"

Guaranteed.

Water "turbidity" is a common way to rate and compare visibility in water. Your test set up sounds like it could provide some good information but turbidity measurements are a way to compare with less subjectivity. Of coarse it does all come down to how well you can see thru the water in your application, but with data based on samples done at different times (after a rain) and at different depths you may be able to compare it to other locations. Like can you get a small sample at Sea World (set in the front row for the dolphin show). Turbidity meters are widely available.

"Yep"... everyone who's ever been around a swimming pool (residential or commercial) will jump at the opportunity to expatiate on turbidity, and the ease of measurement thereof. The original post, tho', speaks of a new "marine tourism business"... ahem... once again, neglecting to add details such as: for sport-divers, submarines (such as Waikiki beach's), or glass-bottomed boats (Florida Keys). Turbidity is certainly important when it comes to how appealing a glass of cold water appears on a hot summer's day...

When addressing issues such as ["True" / "Honest-to-Goodness"] underwater visibility, *MORE* things need to be taken into consideration than have been addressed as yet; including how reflective the bottom sand is ((again ~ reference the link in my previous post!)). Also--- what TIME of day are you concerned with? Night Dives, anyone...?

Hi Skippy,

Check out this website and turbidity instrument. I think that this is what you are looking for. It comes with 25' of cable but you can order as much as you want.

http://www.globalw.com/products/turbidity.html

As our colleagues have suggested the turbidity is going to change depending on the wave action or weather and will differ at different depths. As you go down to the 25 feet (or whatever depth) you will want to take regular interval readings. If you correlate them to weather conditions - temp, pressure, wind speed and direction, and possibly time of year depending on your location - then in time you may have to only monitor the weather conditions and know the turbidity from your records. Good luck.

Like been said already - then skippy can report to his customers everyday, "The water on top measured 50 NTU's (nephelometric turbidity units) at 7am with no clouds, but on bottom it measured 180 NTU's as a cloud was passing over. If ya wanna ACTUALLY know what the vis is then go on out there and learn how to translate this stuff." That'll be sure to bring him a big return on his turbidity meter!

Scuba Divers don't care about turbitity or anything other than the feet of visibility.

All us scuba divers only want to hear is there is 20 ft of vis or there is 10 ft of vis.

Unfortunately visibility can change daily, even hourly so anything short of an actual online picture or first hand knowldege of today's condition is useless.