Alaska's Cold Water Killer

S7, E4: Jeremy Wade searches for more water-dwelling beasts. In this edition, he investigates a recent fatal incident in Alaska's remote and unforgiving wilderness where fishermen have been vanishing without trace for years. Are bad weather and boating accidents the only culprits, or could there also be an unidentified killer at large - a cold water monster strong enough to drag a fisherman under the surface? Jeremy ventures through treacherous rapids to the mouth of a river where the icy waters are swarming with hungry sharks. However, it is a bizarre and unexpected beast hauled up from the depths that eventually emerges as his deadliest contender.