Those who are cursed by Davey Jones become fused with various parts of the sea, whether it be creatures, rocks, sea plants. Hell, that one guy was simply part of the ship. And his brain... his brain just sat there... in the open... pulsating... Yeesch.
What I want to know is how Bootstrap survived BEFORE accepting Davey Jones' curse. He said he just sat at the bottom of the ocean after being dropped from his ship, not dying. Then the concept of an immortal curse came along. Huh?