They're actually made of plastic not paper, so you can go swimming with them. On a side note the price of precious metals in AUD is much more stable than USD as the exchange rates seem to fluctuate together.
There is certainly a belief among some in the U.S. that AUD is a kind of proxy for commodities, I don't know how close they follow each other because I haven't paid that much attention personally, but I've heard that before.
