Acrtually, fat helps fill in those extra ridges and makes you much more hydrodynamic, like a seal or a porpoise.

Do you think those washboard abs and ripped muscles are helping or hindering your profile in the water?

And while I agree with you that body position+technique are far more important than fat, at competitive levels nearly all swimmers have good body position and technique. At the world class level for marathon swims, that's absolutely certain. At that point, having enough body fat to smooth out your ridges as well as give you a teensy flotation edge may be the difference between winning and losing in those long swims. This can also be seen at play even in local pools with nonelite swimmers - I'm sure you've seen the very obese yet surprisingly speedy fat male or female who looks like they could barely run as they are so faf and heavy, yet are surprisingly fast in the pool, even with sloppy form. I had a gal next to me last week who was 5' tall, 210 at least, big fat belly, crappy, sloppy pull for sure, but almost keeping up with me at 1:40/100 despite clearly doing workouts of <1000 yds, and not at high intensity. There is no other factor than fat that was helping her - take that fat away and she'd def be a 2:00+ swimmer given her form flaws, which were being compensated for with her generous buoyancy and round form (which was probably more hydrodynamic than mine - I have the washboard abs.)

There's a youtube video posted recently of one of the fastest HS swimmers who swam nearly fast enough in an event to win an NCAA Div1 race if he posted the same speed, and while he's not fat, he's far from ripped.