10K open water swim at the olympics...
 

This would be brutal. I once did three miles in a pool in a little over 1 1/2 hours and I would gladly spend six hours on my bike before I did that again.

I would love to enter some Open Water swims as I train with some who've competed at Nationals and Worlds.

It's really not that bad as all you need to do is to draft off somebody and get yourself into a rhythm. 5K is the shortest open water with 10K next and I believe they have 25K and 50K races.

I've done a few open water swims during tris. The only thing I got was a few sharp kicks in the head; no draft. It was pretty brutal, especially for a weak swimmer. I always bail out of the melee and head to the outside of the pack or drop way back. Basically just try to not drown before the bike leg.