As it happens, I can swim quite well, and I don't fly helicopters.
But, I can't recall ever living anywhere that swimming lessons weren't available cheaply and locally. If I was in that position, I'd **** learn to swim, just as at other stages in my own life I've learned numerous other skills that whilst not absolutely required were of real or potential use to me.
Strikes me that some polite encouragement might be in order. If he's embarrassed about being unable to swim, then polite but anonymous help can be a face saver, for example leaving details of a slightly out-of-town swimming course for him.
The thing to avoid, just because the bloke is human like anybody else is direct confrontation or anybody ordering him.
G