My dad has been saying this from the beginning. This is a FLOATING platform. It is kept level and floating with ballast that is shifted as necessary by computer to maintain stability. If all power to the rig is gone and 5 boats are spraying it full of thousands of gallons of water an hour, it was GOING to sink. Had they used what they were supposed to, foam, this might not have happened.
Inquiry asks: Did fire crews cause BP rig to sink? - Disaster in the Gulf - msnbc.com