Bikini Atoll is the marker of where Bikini Bottom is located. It has been seen as just a small island with three Coconut Palm Trees, and is seen at the beginning of almost every episode. The only known locals are the two seagulls that attacked SpongeBob and his friends in the episode "Pressure." In many episodes that involved breaking the surface, or flying out of the water, the island is shown in the background.
When SpongeBob and the gang break the surface, they become puppets on sticks, or live action characters (SpongeBob turns into a real kitchen sponge, Patrick into a dried starfish, Sandy a squirrel puppet with a helmet, and so on). It also appears in a scene in the SpongeBob Theme Song. In the 1940s and 1950s, it had been a place for nuclear bomb tests.
Except for the occasional seagull or pelican, it is uninhabited.