You’d be surprised (maybe not) at how many of holders’ people don’t know how to swim. I’ve spent time over several summers teaching kids something we used to take for granted.
My dad was in the Navy in WW II. The ship’s chef was black and didn’t know how to swim. He and some of his fellow sailors thought they would teach him so they threw him overboard. Said he stirred up a lot of foam so they had to haul him out. Didn’t learn how to swim. I never thought to ask him how his next meal tasted.
Guys I know on the Chicago Fire Dept. have a quite insensitive term for them - "rockfish".