The only time they do feet and hands tied is drown proofing, and the only time the instructor tries to drown you is during ‘life saving’ (or whatever BUDS calls it, in SWCC school it was called water safety) and also during pool comp in second (dive) phase.
And it’s the Pacific. The water is always cold. Having done both, I’d rather swim in cold water versus warm any day of the week and twice on Sunday. The pool at RTC was kept around 80 degrees since the instructors were in there for hours at a time. Swimming laps in it felt like swimming in soup (the water even felt thicker, which I’m sure was mental).