Possible Clues:

• Fitzgerald hero takes the plunge?
• Wreck explorer
• One jumping off board
• A plunger may work under water
• Going down, he may be protected by the bell
• He'll sink to any depths for money
• Up to six in the red, so he's got to get down to it
• A penguin, perhaps - one of several!
• Navy Seal, e.g.
• Olympic athlete