Okay, I learned the song from a Stan Rogers recording, and I heard him say "bones" rather than "booms" - have we established that the term in question is defintely "booms" (and that Stan presumably got it wrong or had a moment of mispronunciation)?

(I'm merely an armchair sailor, and even in my armchair I usually don't venture more than a few feet from the living-room walls, even though I know it's far safer out in the middle of the floor, especially in stormy weather).