Possible Clues:

• There's nothing in an apartment to keep one off the bottom
• John Galt was interested in its legatees
• On the sea
• Not grounded for the angler
• A launch, aimlessly drifting
• Somewhere to live, featuring porthole, on a ship
• Old, in a bedsit perhaps, keeping one's head above water
• Buoyant: solvent
• One part of carnival procession on the water
• With one's head above water