my heart is a glorious machine;

Well... seeing as this has only just very recently come out, it might be a bit too modern, but it certainly doesn't seem very typically mainstream to me. Anyway, it's called "Into the Ocean" and it's by Blue October, and it specifically references drowning, the ocean, and it seems to me to have tints of lost love as well. I've lately become rather fond of it. I would send it to you, but it's protected... actually, are you authorised on my iTunes account? I can't remember. Anyway, that's the only thing I can think of right now.