Aquarium diving/weighting

[kwesler]

For the physics minded on the board...

I jsut started diving at the NJ State Aquarium.When I geared up the first time, the Dive Safety Officer asked me how much weight I planned to use. I told him 12 lbs, which is 2# more than usual-I figured with the new environment, and shallow depth (most of the tank is 15', there is a section of 24') I would add a few pounds-I also was wearing a 5 mil jacket and john, rather than my usual 5 mil jumpsuit.

The DSO told me to put at least 20# on my belt. The other divers all told me they use at least 6-8 lbs more than in the ocean.

Sure enough, even with 20#, I had to fin to get down. I am athletic 5'10 160, and many of the other divers are also lean.

The salinity, while slightly higher than the ocean CAN be, is still the the normal range.

Can anyone explain this to me? 760,000 gallon tank, if that matters.

Ken

 

[cudachaser]

You need around 4# more than normal seawater. No one has ever been able to explain the anomoly. They do inject copper into the water which may increase the specific gravity of the water, but I can's imagine that would change things that much. My theory is that that the induced currents and shallow water causes a diver to hydroplane a bit if you try normal swimming in the tank

 

[kwesler]

ok-I'll check on the copper next time I go (2 weeks). This tank has no motion to the water. I think I heard someone say it was originally planned to have it, but they never implemented.

Ken

 

[SueMermaid]

Oh, I am so jealous. How did you get that gig?

Can you bring friends?

 

[kwesler]

indeed...although I think some of the volunteers are surprised at first at the amount of cleaning etc. that goes with the diving-just like crewing a boat!

I was taken as a guest on a dive a year and a half ago, and kept an eye open for when they did recruiting.

You must go through an interview, then a written test, then a pool test with and without gear, then a comprehensive physical. None of it a big deal, but time consuming...

I can take a guest, but not for 6 months...

If you are interested, PM whatever info you want them to have, and I will be happy to give it to the Dive Safety Officer, although I am sure you can just call them, or email them through their web site.

Ken

 

[roakey]

I'll tell you how it works out the opposite way -- I'm going to be diving Hawaii in early July, using the gear (which hasn't ever seen the open ocean) that I dive an exhibit at our local Aquariumn. The environment is more-or-less is Hawaii, water in the mid 70s and I dive it with a Henderson 7/5 and hood (mid-70s may sound warm until you're in the water for 1.5 to 2 hours!) and wear about 22-23 pounds.

I know our copper level is low, because it pisses off the cartilagenous fish. In fact in one of the other exhibits when they have to do a copper treatment they actually remove the rays and put them back in the quarantine. In the exhibit I dive the sharks are too big for that, so when they have to treat with copper (only once since I've been diving -- 2 years) we just have to keep an eye out because we know they're grumpy.

Aquarium diving is a kick, isn't it? One of the first things I learned is NOT to smile back when you wave at the kiddies -- no one can tell if you're smiling or not, and it floods your mask!

Roak

 

[radagalf]

Is the display you're diving in colder/warmer than the ocean you dive in? Different water temperatures give it a different density, unfortunately it isn't a strict colder, it gets heavier, as we all know ice floats. However, depending on the salinity and the temperature you can get a range of water densities, thus altering your buoyancy. I would check these two variables.

 

[kwesler]

The tank I dive is the shark tank as well-sand tigers, browns and rays, so it is likely they do not add copper, based on Roak's comments.

The water temp is 68 degrees. My weighting, with the obvious adjustments between wet and dry etc., has been consistent between the 70-85 degree warm water diving I do, and the 38 degree dives I do, so I do not think temp is the issue here...

Anyone else with thoughts? I feel better-I thought I was missing something obvious!

Ken

 

[Scottri]

I dive in the Oregon Coast Aquarium and use the same amount of weight I use in ocean dives. It's a cold water environment (50 degree water), I don't know if that makes a difference. The max depth is 27 feet in all three exhibits and I don't notice any difference in any of them. I use a drysuit with the same undergarments I use in OW.



Scott

 

[roakey]

roakey once bubbled...
I'll tell you how it works out the opposite way -- I'm going to be diving Hawaii in early July, using the gear (which hasn't ever seen the open ocean) that I dive an exhibit at our local Aquariumn.

I found no significant difference in weighting. I did drop a couple pounds, but that's probbly due to other factors.

Roak