passport security!

now people here seem to place a lot of emphasis on keeping your passport on your person at all times. i understand this. i really do, and don't doubt for a moment that i don't. but what i can't understand is just what the heck happens when i say, want to take a refreshing dip on a hot sticky day during my stay at corfu for instance? does my passport and money belt come too to cool off themselves? something tells me this isn't really logical. there must be somewhere to place such valuables in these kinds of circumstances.

anyone?