This island seems as if it is deserted, but it isn't really. Everyone lives in a "reverse aquarium" inside the island. The island frequently lowers into the ocean, then coming back up. In Island of Legends, a group of Artimeans go to this island to save Sky's mother, Copper, from the island.
In Island of Fire, it is said that the volcano at the center of Pirate Island acts as a heating system for the inhabitants.
Whenever the island is about to come up from the ocean, Pirate Island will shake violently due to the volcano. Seats will pop out from walls within the aquarium and all the inhabitants will sit on them and put on seat belts to ensure they don't fall and injure themselves.
Pirate Island has a large aquarium where rare sea animals are kept. The pirates used to have a giant electric eel who helped them catch these sea animals.
Workers who attempt to escape from Warbler Island are sent to Pirate Island to work as slaves.
The pirates in Pirate Island occasionally trade with Queen Eagala. It could be assumed that they are 'friends'.