Cathedrals I

You enter through a dark hole and the cavern opens up in front of you, lit by skylights in the lava roof that put turquoise beams through the water with fish silhouetted in them. The centre of the chamber is the altar, a fallen block of lava rock, and it is the reference point everyone works around. PADI puts the maximum depth at 21 feet (6 m), so gas is rarely the limit here; buoyancy is, because there is rock over your head and silt under your fins.

From the main chamber the group works into the side chambers, the confessionals, which regularly hold resting sharks, pufferfish, crabs, eels and nudibranchs. The way out is the shotgun, a lava shoot at the back of the cavern that spits you into open water. From there the dive finishes over the coral gardens and lava formations outside, which is where turtles and the occasional manta ray turn up.

Getting there is part of the day. Several Maui-based operations run trips from Lahaina to the sites along Lānaʻi's south shore, a boat ride of about forty-five minutes each way, and Trilogy Ocean Sports is the only full-service dive operation based on the island itself. Whichever boat you are on, listen to the briefing: the layout of a cavern like this is not something you can read off a chart beforehand.