Two divers hang beside the altar, a fallen slab of lava at the heart of a submerged cavern in the Cathedrals, off Lanai in Hawaii. This is an old lava tube, and where the roof has broken open the sunlight pours down in hard blue shafts, catching the divers' rising bubbles in silver columns. More light scatters through the back of the cave, which is how the site earns its name. We had crossed from Maui that morning and dropped into the cavern, and while the two of them bent close to read the nudibranchs along the altar rock, I hung back near the wall to keep the whole room in the frame. From there the divers read as small dark shapes under all that falling light. These waters sit at the edge of Lanai's Manele-Hulopoe Marine Life Conservation District, where the reef and its residents are left undisturbed.
