Rikoriko Cave

Rikoriko is a sea cave so large that tour boats park inside it and singers test the acoustics from the deck. Underwater, the scale inverts the usual cave experience: instead of squeezing through passages, divers hang in an auditorium of dim green light, following walls where the daylight species of the outer reef give way, meter by meter, to the low-light specialists usually found much deeper. The famous local trick is finding gorgeous pale nudibranchs and cup corals in a few meters of water that behave as if it were fifty. Glancing back at the entrance, a blue-white cinema screen with boat hulls floating across it, is the image everyone surfaces talking about.

اللحظة التي جئت من أجلها: Diving inside one of the world's great sea caves, deep-water species in the shallows, the glowing entrance view

التضاريس: Vast sea-cave dome with boulder and wall habitat fading into darkness

نقطة الدخول: Boats motor straight into the dome to drop divers; the dive works the walls from the bright mouth into the gloom and back.

المخاطر: Darkness disorientation at the back of the dome and boat traffic at the mouth; keep the entrance in sight or a torch on the wall.

الحفاظ على البيئة البحرية: Reserve rules apply inside the cave as out; take particular care with fins over the low-light wall life.