These men and women (though some are but teenagers) are water equivalent of runners. Some sprint, some do middle distance, and some--our kindred spirits--do long distances.
But the one thing the swimmers all have in common with each other, in sharp contrast to the stereotypical lean Ultrarunner, is that they are all shaped like seals. Or maybe sea lions (I can never keep them straight).
Not that there's anything wrong with that. Just an observation.
As for me, I have done lap training in pools for cross-training, and I'm a decent enough swimmer, but I Just. Don't Like. It. At all. There's no worse feeling in the world for me than being out of breath in the pool. I liken it to waterboarding, if to which I were subjected I would sing like a canary before the first drop even hit.