10K

Interesting interview with distance swimmer Micha Burden at Competitor Magazine (link courtesy of the17thman):

PH: Everybody's like, "open water swimming, that's no big deal, and 10K? That's 27 minutes at the Olympics for the guys who run that!" How long does it really take for the best swimmers in the world to swim 10K in open water?

MB: Well it depends where you are, but it usually takes about two hours.

PH: Wow, so do you have aid stations? What do you do for nutrition? Do they just throw it at your mouth, like at Seaworld?

MB: Actually they have feed-boats, usually one or two, on a pontoon boat.

BB: You don't want to stop though, how do you do that?

MB: Everybody stops, because you do need to get some calories and some liquid in your body. It's really hard to maintain that pace for two hours! A lot of people will put gel packs in their swimsuits, and they actually make these little contraptions with a stick and a cup – basically they lower it down to you and you just swim by and grab the cup, and they usually mix a gel pack with a little bit of Gatorade in it and you just take the shot really fast and keep swimming. I think in America, since we don't have that much experience, the first couple of races people wouldn't stop at the feeding stations so it was a risk if you stopped because you might lose the pack. But in the international races everybody knows they need to stop so everybody stops, and if you don't stop and try to break away you're probably going to run out of gas and the pack is going to eat you up.