Castaway Island is an island that is located off the coast of Booga Bay on Shark Tooth Island. You can only reach the island after you've put the Great Booga Shark to sleep to cross the water. You will find Professor Hammerhead and the woman's son stranded there. After leading them back to the mainland, you will receive the island medallion from the boy's mother.
The island appears as a large pile of sand with a few palm trees, a small makeshift hut with a clothing line, a few broken crates, some coconuts, and a bamboo fishing pole lodged between two rocks. The word 'HELP' is also spelled out on the shore in sticks.
- Despite the fact that the bottom of the word "HELP" is underwater, the branches creating the word still remain intact with none being washed away from the current (very weird).