Im not really afraid of anything, as at least one person who knows me will point out but...
Drowning in a cave. Water levels rise and rise while you continue to explore. After a couple hours you decide it's about time to head home so you check your air. You start swimming back. Going through a tight space you bump your light and it goes off but you keep moving because you know the cave fairly well. After a couple minutes you hit it and it comes back on so you look around. Suddenly you dont notice anything familiar and start to worry but you keep going.
By now you realize you should be back. You check your air again and it's running out fast. So you come up in an air pocket in the cave, you light goes out again. The tide continues to come in and you start to panic...
3 weeks later another diver finds a lone body floating in the cave. After dragging it back they notice the fingertips are worn down to bone from where the person tried to claw their way out of the rock...
In other news, anyone have OED access they'd like to share?