| || Well, that's not its name ... but ...
The term "Beach cave" has not been confirmed by official sources.
This beach cave is a system of underground caverns beneath an island in the eastern Fire Nation. Team Avatar stayed here for a short time during their travels through the Fire Nation, and it was the location of a large dance party conceived by Avatar Aang for the attendants of a local school.
Team Avatar stayed in the cave for a short time during the summer of 100 AG. Here, Katara envisaged the idea of finding Fire Nation clothes and accessories so they would not have to hide there during their stay in the Fire Nation. In the morning, they left the cave to search for new outfits in a bazaar.
Unknown to the rest of the group, Aang accidentally enrolled himself in a local school. He did not return to the cave with everyone else, which worried his friends. Aang returned that evening and told everyone the surprising news that he had gone to school. He encouraged his friends to let him continue going to school so he could learn more about the Fire Nation, to which they reluctantly agreed.
That night at the cave, Team Avatar organized a secret dance party for Aang's friends at the school. Many students came and although they felt a bit uneasy about dancing at first, Aang was eventually able to persuade them into expressing themselves in the fullest. He impressed everyone with his dance moves and performed some of them with On Ji and Katara. However, the party was interrupted by the Headmaster, who was informed by Hide of the illegal event. He and other school officials searched the cave for Aang, whom they intended to send to reform school, but failed to find him in the vast crowd of students. Team Avatar escaped the cave through a back exit and flew away on Appa.
The beach cave is located on the coast of a small, crescent-shaped island. It lies at the foot of a grassy hill that sharply gives way to a rocky, black beach. The area of the hill in immediate vicinity of the cave's entrance is a steep, partially inverted cliff, though it is a more gentle slope further away from the entrance and up. The cave and the surrounding area is mostly uninhabited and devoid of fauna, though a few toucan puffins, cavehoppers, and iguana seal can occasionally be found.
The cave's interior consists of black rock, which is fairly smooth on the floor but much more bumpy and rough along the sides and ceiling. In certain places along the cave wall, the rock is sharp and pointed, though this is seen only sporadically. The entrance is large and shaped roughly like a half-circle. Overall, the cave is spacious and can comfortably accommodate many people all at once.
For the dance party, Aang and his friends decorated the dreary cave to make it look more inviting. They lit several candles and scattered them across the cave wall to enhance the lighting. Toph created circular, earthen risers for a musical band to perform on while Katara made fountains.