As we know, double x chromosomes are never wrong and SWMBO pointed out that masts extend above the waterline and KEELS extend below it (remember Australia 2 infamous winged keel).

She's not right is she?

Well, when foiling, the mast is actually above the water line...

If you were slogging along without getting onto a plane, I guess it would feel natural to call it a keel.

Everyone wins!

You are better off loosing this argument.
And any other :)

I think once you're foiling the whole deal is no longer a boat, it's an aircraft. So I'll go with vertical stabilizer.

This confusion is even worse for windfoiling. Sail mast or foil mast? Huh?

Some people use the word "strut" for the foil mast.