[brucecw]

How do underwater divers etc tolerate the 30 degree east coast waters?

Wet suits and the like. They can't keep you going indefinitely of course but can slow the loss of body heat considerbaly.

[rickylc]

Actually, it's "dry suits". They seal air in around the body to prevent heat loss. In really cold conditions, argon gas is used to fill the space. I'm a biologist working in Lake Michigan and have to dive regularly to do my research. The first time I used a dry suit was for a dive I needed to do in late November. I was warmer in the water then than many times I have been down in August. Any time you dive below the thermocline (below the warm surface layer of water, 10-20 meters)the temp is around 40F and "dry suits" are the way to go. Once you are in the water in a dry suit, it doesn't matter if it's August or December.