The shock of jumping into COLD water can give us older folks a heart attack, too! No thanks--I'll do my little sponge bath in the tent with the little water left over from dinner in my kettle. It won't be hot but at least it's not cold. If that means I'm not a "real" backpacker, tough ****. Remember that back in pre-plumbing days, sponge baths were usually the only option for everyone!

There's also the issue that residue from sunscreen, bug repellent and lotions on hikers' skins is, per biologists, one of the primary reasons for the decline of amphibian species in popular hiking areas. You might want to do a quick sponge-off of that stuff before jumping in. Forget soap; that kills aquatic species, too. (That's not for you, W_D; I know you're anti-soap, too!)

I did do a little swimming in Lake Superior once, 8 years ago. It wasn't warm, but it wasn't nearly as cold as our mountain lakes! That's the only time I could persuade my late dog Hysson to swim, and it was the last--he swam out to me and then proceeded to climb on top of me, in water up to my armpits! After that, his only swimming maneuver was a quick turn to shore.

I suspect that after freezing over this winter, Lake Superior will be colder next June than when I was there!