From http://science.howstuffworks.com/environmental/green-tech/en...:

"Many geologists suspect that gas hydrates play an important role in stabilizing the seafloor. Drilling in these oceanic deposits could destabilize the seabed, causing vast swaths of sediment to slide for miles down the continental slope. Evidence suggests that such underwater landslides have occurred in the past, with devastating consequences. The movement of so much sediment would certainly trigger massive tsunamis similar to those seen in the Indian Ocean tsunami of December 2004."

Sounds dodgy to me :(