Marine Cave is a small cave located on Nabiki Beach. The cave has three rooms in which various Pokémon can be found and also on its first appearance, a Gigaremo unit.
Going to the Marine Cave will be the first mission when the player becomes a Ranger. The player is accompanied with Crawford to investigate the mysterious noise that is heard here. It was later revealed that it was a red Gigaremo unit and that Team Dim Sun was responsible for it.