Lost Lake Cave – West Coast & Remote Sites

Site Overview

Lost Lake Cave is a unique blue-hole-like sinkhole on Christmas Island connected to the ocean through an underwater passage entered via a spectacular coral-encrusted archway. This extraordinary geological formation creates one of the most unusual and memorable dive experiences available anywhere in the Indian Ocean region. The approach to the cave begins with a swim through the coral archway which is encrusted with diverse hard and soft coral communities creating a colourful gateway into the underground world beyond. Inside the archway, a large cavern opens up with a sandy floor and high ceiling creating a spacious underground chamber that feels both awe-inspiring and intimate. The cavern walls support encrusting organisms and delicate formations that have developed in the stable protected environment over thousands of years. Schools of glassfish shimmer in the torch beams while soldierfish and lobsters occupy the darker recesses of the chamber. The blue-hole-like nature of the formation creates unique water chemistry conditions that support specialised cave-adapted organisms not found in the open reef environment. The entrance through the coral archway is itself a highlight of the dive with the colourful coral formations framing the dark passage beyond creating a dramatic photographic composition. The combination of geological uniqueness, atmospheric cavern exploration, and the spectacular coral archway entrance makes Lost Lake Cave a bucket-list dive experience for advanced cavern divers visiting Christmas Island.