It's also a collateral duty for enlisted as well, so the division that owns the swimmer will be giving him up a few times a week for him to go swim and keep his quals current...We've had to let other ships "borrow" our swimmers on a number of occasions because they fucked up and either didn't give their guys time or didn't monitor the program's maintenance...usually only when you bring up the fact you won't get to go underway if you don't take care of this right now.
As much as bagging on the AF is fun, when you have 3-4 "jobs" on a ship, it's easy to appreciate the idea of dedicating a "pro" to each job instead of establishing collateral duties without a clear CoC.
I had a share of this fun during my time in Shoegatory, as I was 1st Lt and so somehow everything pertaining to getting away from or onto the pier eventually became My Problem. Instructions say "thou shalt have X qual'ed rescue swimmers" in order to get U/W or do small boat ops. Doesn't specify E or O, and if an officer does manage to scam a slot to RSS, it's because he's trying hard to get it. As mentioned, I had a JG on my boat who went and qual'ed, but he was a big triathelete, waiting to class up for BUD/S, etc., and he scammed a spot during our post-deployment yard period.
Usually captains want fairly experienced petty officers who're PT studs and smarter than the average bear to go to swimmer school (less chance of them dropping out and thus wasting a school slot). And those guys are also usually LPOs and other persons who are hard to spare for a months-long school.
The problem with the AF "full officer promotion path for every conceivable job under the sun" philosophy is that eventually you wind up with a bunch of O-3's and O-4's trying to "stand out" and creating busywork for everyone within reach. I've seen AF Captains doing jobs that the Navy would have made contractor years ago. Seriously, I'm surprised they don't have a Handing Out Basketballs at the Gym career track.