I lived in 3 different islands with tons of boats (from cruise ships to yaughts, to tankers, to cargo), have never heard "the hum" (nor has anybody else complained or mentioned any of the thousands there), don't even know what you're on about...
I literally haven't thought much of it until reading this article, other than passing observations. For example, I've noticed it's not audible in every house, and usually not audible on the ground floor when it is audible on other floors.
What exactly about "the boats" would it be? The motor? The propeller?
Doesn't sound like a thing...
One unfortunate effect of the name "the hum" is it kind of implies a single source. Realistically, it's probably a whole collection of sources, including some real physical phenomena, and some tinnitus-like audio hallucinations.