Yes, I know of one highly unofficial test...
...because I myself conducted it in the unheated swimming pool of my best friend's apartment complex in Los Angeles. <img src="/images/graemlins/laugh.gif" alt="" />

This pool had so much shade that it got sun for, at most, half a dozen hours each day and stayed (at least to this Texas boy) very very cold at all times. My California friend rarely swam in it, because, for most of the year, it stayed too cold for her as well.

I was visiting her a couple of years back after having participated in Doug's liferaft testing. I had tried on an exposure suit for the first time during that testing and so had this kind of stuff on my mind. I had a couple of Space Bags in my Jeep and realized it would be a great time to test if they would work like the Land/Shark bag is supposed to. (It's a pity I didn't have one of those with me so I could compare them in the water.)

I ripped the first one by trying to unfold/deploy it in the pool. It still helped to keep me warm, but the rip was allowing way too much water to exchange, so I threw it out and tried again. These bags are quite fragile and can only be used when you can be calm and gentle enough to rest in them... no moving around or bumping into debris. You will have to have some flotation aid... treading water will rip them.

I unfolded the second bag on land and got inside it. Then, I refolded it as tightly as I could and put it in a ziplock bag. Deploying this one in the water proved much less difficult and I managed to do so without damaging it. I had no PFD on, and so, inevitably, my attempts to balance on floating pool toys for buoyancy eventually led to me stick a foot through the bag. I'm fairly certain that, had I been able to simply float with a vest, the bag would have lasted indefinitely.

Even with the small hole, I could tell a notable (translation: wonderful) increase in the temperature of the water in the bag with me as opposed to the water out in the pool. I was actually able to get comfortable and stop shivering. It's not very scientific, but that's just got to matter in delaying hypothermia. Getting out of the bag was a renewed shock ... I had become used to the temperature inside my bag o' water and the pool water was so much colder.

Stay safe,
J.T.