Into the Blue
"Raptures of the deep" (nitrogen narcosis) is a condition in scuba diving where an underwater diver feels elation and euphoria from a buildup of nitrogen in the brain. Though not physically dangerous on its own, divers who succumb to this condition become so intoxicated, so convinced of their invincibility, that they gleefully dive to their deaths - they swim too deep for their equipment or abilities, refuse to surface or simply remove their breathing equipment altogether. Either way, they perish. And when they die - here’s the creepy part - they die happy.
This is a song about nitrogen narcosis. For added dimension, it's sung from the perspective of a sinister, intoxicating killer, lending it a dark, romantic angle that speaks of any bad relationship or self-destructive obsession. Check your gauges. Enjoy your dive.