Mark is despondent as he has not just lost his new pet, Marco Polo, but his old pet Ben. Frank from Seaquarium takes Mark and Tom out on a boat to find Ben and Marco Polo. They spot Ben on a small island and as they get his attention and he swims for the boat he is threatened by a shark. Marco Polo comes to the rescue and nudges the shark away from Ben. Ben climbs a ladder to get onto the boat, and Marco Polo is returned to Seaquarium.