Possible Clues:

• On water
• In good financial shape
• At sea, drifting aimlessly
• There's really nothing in an apartment like this to keep one on top
• There's nothing in an apartment to keep one off the bottom
• At sea - in circulation
• For the angler it's on the top - for the ship, not on the bottom
• Not going under
• Nothing kept in an apartment aboard ship?
• A little money to start business makes one solvent