It is a sand island in the middle of the ocean. Its most notable landmarks are the three trees that inhabit one side of the island. It appears small, but in reality, it is much larger and appears small because of an optical illusion.
On the other side of the island there is a forest filled with an array of wild life and a skeleton who formerly guarded the Magic Book.
Bikini Atoll has been around for millennia. The trees that inhabit the island have had its ancestors during the times of prehistory.
At one point, Davy Jones was either on the island or at least had the Magic Book which formerly resided on the island.
After Sandy is frightened by SpongeBob and Patrick (as ghosts), she leaves Bikini Bottom and travels back to Texas via an acorn-shaped rocket, which launches out of the ocean and to the landmark of Austin, Texas.
In the second level, Plankton and Jimmy Neutron have the chance to enter a pipe, which leads to Bikini Atoll. A Krabby Patty cheat trophy is on the island.
In "The String," the island was presumably destroyed when SpongeBob unraveled all of Bikini Bottom and the Milky Way with the string.
The episode "Mrs. Puff, You're Fired" includes the footage from "No Weenies Allowed" where SpongeBob is flung out of the water and back in again.
Bikini Atoll was an island that was used for nuclear bomb testing in the 40s and 50s.
Starting with "Lame and Fortune," a CGI model of the island is used instead of the filmed island.
This is because the original model island is buried somewhere deep within the Stephen Hillenburg Storage Facility, where he rents to pile things that he doesn't have room for in his house.
When the island is shown at night, a human finger is visible in the water to portray a reflection of the moon. According to the "Christmas Who?" audio commentary, Stephen Hillenburg filmed the Bikini Atoll island at Steve Belfer's house in his friend's pool in California.