Island Monster is a huge anglerfish-like creature that can camouflage to an island and uses its antenae light as the Sun. When Marina was getting to a fight with Sinbad, she peels one of the creature's skin and prepares to slam it on Sinbad. Before she could do that, the "island" begins to shake and the "Sun" was the creature's antenae light. The Island Monster opens it's eyes and Rat accidentaly falls in and Spike begins to lick the monster's eye. The characters run for the ship and the monster begins to move. Sinbad throws a harpoon at the creature which makes the creature to drag them to Eris's hideout. By dawn, everyone started to feel a little sea sick. Sinbad cuts the rope and the creature was set free.
The "Island Monster" in Sinbad seems to have a lot of similarities to the mythical sea monster Aspidochelone. The Island Monster, like Aspidochelone resembles an island, complete with trees and greenery.