Before Air travel became the norm, people used to travel by water, and unless you know how to swim, you may drown for whatever reason.

The educational institutions didn't want all that effort wasted so they started requiring swimming education for people.

Or something like that, don't quote me haha

I almost didn’t get my MIT degree because I had neglected to take the swimming test, though I’d been swimming since childhood. I finally casually went in to take it and was told “you’re just under the wire, we’re closing it tomorrow for renovations”.

I don’t know if my leg was being pulled or not as I was already working full time and just finished my degree out of principle (and good thing I did!)