A renegade sea otter is terrorizing California surfers: 'It's a little scary'

But about 90 minutes into his session, he was attacked — by a sea otter. An adult sea otter can weigh 30 to 100 pounds, and reach 5 feet in length. "I would not characterize this as a common behavior for sea otters. That otter, Fujii said, had probably been fed illegally by people — a common trigger for this kind of aggressive behavior. Fujii said there are about 3,000 sea otters living off the coast of California.