Temperature In Degrees Fahrenheit
Density per ft3 (lbs)
At 32 degrees or freezing point at sea level 62.418
At 39.2 degrees or point of maximum density 62.427
At 62.0 degrees or standard temperature 62.355
At 212 degrees or boiling point at sea level 59.830
Not sure how valid the data is
http://energyconcepts.tripod.com/energyconcepts/water.htm but ut is consistant with other sources I found on the Internet.
Now take an example of a 5ft3 person and look at the buoyant fources applied at a few different temperatures (it is the principle that counts).
39.2F---> 62.427lbs/ft3 x 5ft3=
312.14lbs
62.0F---> 62.355lbs/ft3 x 5ft3=
311.78lbs
These results are the buoyant forces applied to an object (diver in this case) that is 5ft3. So the difference going form ~40F water to ~62F water would be about .37lbs.
Given that this would be a rather large diver and that an extreme temperature shift you could say it is relativly insignificant.
Now take this to the next step and apply how this could in any way effect a diver. Given that the 62F water will be at the surface and the 39F water at the bottom and you are probably wearing a thick wet suit (in anticapation of the COLD water). As you go down the wet suit will compress and as a result you will displace a smaller volume of water. The fact that the water will be more dense will actually assist you in this case. Note that the suit compressing will have an overwhelming effect on your buoyancy but the density will play a very small role. Also note that all these calculations are based on fresh water.
As always I reserve the right to be totally out to lunch and if so please let me knw as I am sure you all will