New Kid's Questions #4 - Water temperature vs bouyancy

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caseywilson

caseywilson

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Location
Ridgecrest (SoCal)
# of dives
25 - 49
What effect does water temperature have on bouyancy? Or, put it this way, with all other factors staying the same, except going from 82F to 60F, will I need to add or remove weight to be neutral? Or is it so neglibile as to be ignored?
 
I wouldn't give it any thot except for changes in salinity and wetsuit.
 
I agree. The changes in the water due to temperature is not going to make any difference in weighting. The change in thermal protection, however, will make a huge difference in how you weight yourself.
 
If you think about it, density changes are measured in degrees Kelvin -- when you are going from 300 K to 288 K, the proportional pressure change is very small, even for gases, which expand and contract a lot. For liquids, where expansion is comparatively minimal, the difference is even smaller.

The bottom line is that buoyancy will be impacted far more by the different exposure protection you will choose for those two environments, than it will by any changes in water or gas density at the two temperatures.
 
Neat question.

The previous posters are correct. The water density will increase, but only very slightly. As you go from 82° to 60° F, water density will increase by approximately one-third of one percent. Hardly noticeable.

Now if you go from balmy to ice diving, and have your lead really dialed in, you might need to add a bit. In that case the density change can exceed four-tenths of a percent and you might want to consider adding a pound.
But of course in that case your thermal protection will change dramatically and the one pound added for increased water density will be swamped by other changes.
 
casey as posted above the difference won't be noticeable but you WILL change your thermal protection so will need to adjust boyancy to suit.
 
Looking over my logs it seems I'm much more buoyant in warm water vs cold water. Even taking into consideration the exposure protection I use...

Example: 12 pounds, 7mm wetsuit, 52f water here in Canada vs 12 pounds 3mm wetsuit, 82f water in Belize... obviously the warm Caribbean water is more buoyant than the cold Canadian water.

I don't know whether the HP100 and fresh water at home makes any difference vs the Al80 and salt water in the Caribbean..... Or maybe I've even lost weight myself...
 
ubp_sanity:
Looking over my logs it seems I'm much more buoyant in warm water vs cold water. Even taking into consideration the exposure protection I use...

Example: 12 pounds, 7mm wetsuit, 52f water here in Canada vs 12 pounds 3mm wetsuit, 82f water in Belize... obviously the warm Caribbean water is more buoyant than the cold Canadian water.

I don't know whether the HP100 and fresh water at home makes any difference vs the Al80 and salt water in the Caribbean..... Or maybe I've even lost weight myself...
Click to expand...

DandyDon:
I wouldn't give it any thot except for changes in salinity and wetsuit.
Click to expand...
You wore your 7 mil in FW and your 3 mil in SW, right? You are more buoyant in SW. I roughly add 8# going from 3 mil to 7, but subtract 4# going from SW to FW.

And the buoyancy of the tanks does matter too. See Scuba Cylinder Specification Chart from Huron Scuba, Ann Arbor Michigan
 
Also bear in mind that, specifically new divers, will often breathe faster when they're in cold water. This could affect your buoyancy. It has nothing to do with the water temperature but rather with your breathing.
 
ubp_sanity:
Looking over my logs it seems I'm much more buoyant in warm water vs cold water. Even taking into consideration the exposure protection I use...

Example: 12 pounds, 7mm wetsuit, 52f water here in Canada vs 12 pounds 3mm wetsuit, 82f water in Belize... obviously the warm Caribbean water is more buoyant than the cold Canadian water.


I don't know whether the HP100 and fresh water at home makes any difference vs the Al80 and salt water in the Caribbean..... Or maybe I've even lost weight myself...
Click to expand...

...plus the fact that in Canada you dive in fresh water and Belize...it is salt water which requires (from the top of my head) about 6 lbs more based on PADI AOW book. You are also looking at about five to six pounds difference between steel 100 HP and a conventional AL 80.

FYI...I need 16.5 lbs 7mm one piece/no hood with an AL 80 up here and was using 22.5 in the Bahamas with same set-up. Diving 3mm, between 14 and 16 in Cozumel using AL 80
 
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