Lanai, Hawaii, United States

Cathedrals of Lanai

The Cathedrals are two large collapsed lava domes off the south coast of Lanai, accessed by boat from Lahaina or directly from Lanai. Cathedral I and Cathedral II are within a kilometre of each other and feature open chambers up to 18 metres deep, with windows and skylights in the basalt that send shafts of sunlight onto the white sand floors and create the stained-glass effect that gives the site its name. Penetration is straightforward through wide openings; the largest chamber is big enough for a class to fit comfortably while still leaving overhead clearance for bubbles to escape. Resident species include white tip reef sharks resting in the side caves, large green sea turtles, slipper lobsters in the cracks, spotted eagle rays and schools of pyramid butterflyfish on the outer walls. The site is weather-dependent: a north or strong south swell will close it, but on calm days visibility regularly exceeds 30 metres. Intermediate certification recommended due to the overhead environment, even though the openings are large.