How many gallons of water does a waterbed hold? That sounds like a disaster to me. Especially if you live in a aparment with litigious neighbors below. I knew a guy who was a junkie who nodded off while filling up a large fishtank. He woke up to the police banging on his door because the tank had overflowed for a good long while, and flooded the neighbors below. Not only was he evicted for the flooding, but arrested and jailed for having a bong on the table when he opened the door. The bong gave the cops probable cause and they searched the place, finding all the drugs he had stashed throughout. Good riddance to bad rubbish.
The moral of the story- don't do drugs, kids! And don't play with knives around waterbeds either.