I was doodling weapons just now, and remembered I had a bunch of initial sketches for the Atlantis weapon. They're quite different from the result and have more batman inspiration.

Anyway, I was looking for good shapes, and I had this idea that under water you might not want to swing weapons, because of the drag - punching, stabbing and shooting will deliver more force. My ideas drifted around guns, knuckle irons and gauntlets.