Dr.Gabe Mirkin’s Fitness and Health E-Zine dated November 7, 2010 features this article titled:

Danger of Swimming in Warm Water

We don’t yet know why US swimmer Fran Crippen died in Dubai, but the most likely cause is heatstroke.  He disappeared in
86 degree water barely 400 meters from the finish of the six-mile
World Cup race.

During exercise, more than 70
percent of the energy used to drive your muscles is lost as heat,
so your heart has to pump extra blood from your hot muscles to
your skin where you sweat.  When you exercise on land, sweat
evaporates and cools your skin to dissipate the heat.  You
produce sweat when you swim, but the sweat cannot evaporate to
cool your body. Read the rest of this entry »