gaining intelligence and anthropomorphic appearances. Joe, the pilot fish, quickly uses the antidote to found a civilization of intelligent fish, intending to launch a revolution. The Shark becomes his dim-witted subordinate. Fly, Chuck, and Stella reunite, accompanied by Sasha, a seahorse who Stella adopts. If they do not find the antidote within forty-eight hours, their transformations will be irreversible. The trio swim to Joe's domain, a sunken oil tanker, where Fly tries to steal the antidote. They are caught and interrogated by Joe about their intent and origins. He demands they manufacture more of the antidote, or the Shark will eat them. The children are imprisoned, guarded by an aggressive, militaristic king crab. Sasha frees the children, who manage to escape. The children decide their best hope is to duplicate the antidote's formula themselves, gathering ingredients from around the ocean. Just as they complete the potion, Joe and his army appear. In a stand-off, Joe drinks the last of the original antidote, transforming his fins into hands. The children try to flee, but Fly is wounded by the Crab, who drinks the new antidote, declaring himself the King Crab. At the same time, MacKrill and Bill pass over in a makeshift boat powered by a water pump. The pump causes an underwater typhoon, sucking up all the army. The Shark eats the King Crab, but is incapacitated when he is sucked head-first into the pump. Chuck remembers that MacKrill has another antidote in his laboratory. Formulating a plan, Chuck plans to carry Fly and Stella through dangerous seawater intake pipes back to the lab. Stella has to leave Sasha behind. The children flood MacKrill's laboratory to reach the potion, but Joe follows, stealing it. Fly pursues Joe into the pipe, tricking him into repeatedly drinking from the potion by challenging his intellect. Joe evolves into a deformed humanoid and drowns. Fly drags the antidote back into the lab, Chuck uncorking it just as Lisa and Anna open the door to the flooded lab. Chuck and Stella become human once more, reuniting with their parents and MacKrill. After a few tense moments in which a stuffed fish is mistaken for the limp body of a Fly, the human Fly emerges from one of the lab's pipes with a broken leg. Some time afterward, the family and MacKrill play on the beach. Sasha appears, so Chuck and MacKrill transform her into an