This video is amazing.
Last November, Salmon researchers working on the Brooks Peninsula were using their remote-controlled mini-sub when it was attacked by a giant octopus. The $200,000, uninsured, piece of equipment was very sensitive and marine biologist, Mike Wood, knew right away the damage an octopus bite could cause. Thus, he reacted instantly with the only defensive weapon their sub had: thrusters. By kicking up seabed particles at the octopus, it finally let go and disappeared.