Cathedral Cave is the tall sea cave inside Motukokako's Hole in the Rock, reached by boat on settled Bay of Islands days. Divers follow a dramatic chamber with light pouring in from above, steeper walls near the entrance, and a shallower back section that makes the cave feel bigger than its footprint suggests. The site is known for stingrays, eels, nudibranchs, schooling fish, and small critters tucked into the rock, while clearer days add the blue-water contrast outside the cave mouth. Although the route is straightforward in calm conditions, it remains an overhead environment in open water and is best treated as an experienced local boat dive rather than a casual swim-through.