How do you get the pearl on mythology island?

Answer 1

Go to Poseidon's realm, using the starfish (from the Museum statue) on the altar in the temple. Pass Aphrodite's test and enter the water. Swim right along the top, down the right side, and left on the bottom of the maze to reach the Gnarly Monster Cave (the Hydra). Up and right of the cave is the Giant Pearl.

Answer 2

To get the pearl, you must take it from the clam. The clam is around the Hydra's Cave, in the ocean. When the clam opens, you swim up to it and get the pearl before it closes.