Circling Rip and Archer.
A shark was able to attack Archer and Rip Riley while Archer tried to swim them both to the surface. It was circling them and then started to attack. Archer pulled Rip's gun and attempted to shoot the shark, but there wasn't a bullet in the chamber. Archer had to drop the liquor in his hands in order to cock the weapon and he then shot the shark in the face. It appears to be an Oceanic Whitetip Shark judging by the rounded fins, white underbelly and fin tips as well as the location which Archer and Rip crashed into the ocean. The Oceanic Whitetip is suspected to be responsible for many fatal attacks on humans, as a result of predation on survivors of shipwrecks or downed aircraft, such as Rip's crashed seaplane.