Thundercliff Cave

Thundercliff Cave is a sea-cave dive site at Christmas Island, consisting of a series of sea caves where divers can surface into air-filled caverns decorated with stalagmites and stalactites. The site reaches a maximum depth of 40 metres and is rated as a technical dive.

The cave system is set within the limestone cliff formations that extend downward from the island's steep coastal escarpments into the ocean. Inside the caves, the passages lead into darkened sections where flashlight fish can be spotted blinking their bioluminescent lights.

In the open water around the site there is a chance of encountering larger pelagic species including tuna, barracuda, giant trevally, and sharks. The dry season, when water temperatures drop slightly due to currents from the south, is noted as the best time for sightings of larger fish. Spinner dolphins are also sometimes seen and may approach the area.