Engineering the Scrooge McDuck money pit

If you watched Duck Tales in the 80s you saw Scrooge McDuck... the greedy bazillionaire duck with a swimming pool full of money.


Thanks wikipedia.

At lunch today, we talked about how you might actually construct a swimmable money pit:
- Use paper money instead of coins, and perhaps put fans into the floor blowing air upward to ensure that you can actually swim in, as opposed to sit on top of, the pile of paper.
- Use coins, but fill the pool with a few feet of mercury first.  Mercury's density is 13.55g/cm3, so just about any coin will float in it.  Thus, a few-inches-thick pile of coins will float on top of the liquid mercury, and you could easily push the coins around as you swam through the mercury.  (That is, before you got mercury poisoning and died)
- Find one of those indoor skydiving places, and determine what coin has a similar terminal velocity to a person.  Then, you can float suspended in the air, surrounded by gobs of money. 
- Put the money inside clear plastic balls, kind of like the Chuck-e-cheese ball pit.

Any other ideas?