There is a cage where Triton is trapped in with a lock on the cage door. Also, there is a bus stop on the edge of the island where people can enter/exit the island. Even there is a phone booth right across from the cage. There is a jungle at the back of the island. There is a mountain next to the jungle. The island is also located across from another island, which is a miniature golf course, with a river between the two.
Role in episode
Triton was locked there in a cage by his father, Neptune. Neptune locked him there for thousands of years until he learned to become a proper god. SpongeBob and Patrick went there to free Triton so Neptune could see him for his 5,000th birthday.
The Island in the Sky may be a parody to Angel Island from the Sonic the Hedgehog series, which is also an island that floats in the sky.