Rikoriko Cave
Depth is the range from the top of the site to its usual maximum; "recommended cert" is the mainstream-agency level operators usually ask for, not a legal rule. Currents and visibility change daily — treat everything here as planning ranges.
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.
The moment you come for: Diving inside one of the world's great sea caves, deep-water species in the shallows, the glowing entrance view
Topography: Vast sea-cave dome with boulder and wall habitat fading into darkness
Entry: Boats motor straight into the dome to drop divers; the dive works the walls from the bright mouth into the gloom and back.
Know before you splash
Hazards: 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.
Conservation: Reserve rules apply inside the cave as out; take particular care with fins over the low-light wall life.
Who you'll meet
For photographers
Wide angle: ★★★★★ · Macro: ★★★★☆ — editors' 1–5 rating of what this site gives each style of shooting