An astute observer happened to be watching the live video footage of the BP rovers working on the oil leak. Reports says that an alarm went off, which was seen by the observer, at which point he/she hit the record button to capture this amazing video of the sea floor literally expanding from what seems to be a methane gas bubble, and subsequently collapsing down on top of itself.
We do not have an official story on this as of yet. Perhaps BP was releasing pressure, but it looks as if a high pressure force came flying up through the sea floor, forcing the floor itself to rise and then suddenly collapse.
UPDATE: Some reports around the web are suggesting that this is movement not of the sea-floor, but the rover/camera itself and is essentially an optical illusion.