Poor Knights Islands

The Poor Knights Islands off Northland, New Zealand, are known for dramatic volcanic topography of sea caves, arches, tunnels and cliffs. When the volcano went extinct it left a rugged landscape of basalt and volcanic rock. Some of the caves and tunnels are above water and some are fully submerged, and arches formed where erosion punched through to the other side of a cave.

Rikoriko Cave runs from about 8 m (26 ft) at the back to over 20 m (66 ft) at the entrance, with sponges and other encrusting life at 12 m. A dead sperm whale once drifted into it, and part of its lower jaw still lies in the cave. Maomao Arch cuts through Tawhiti Rahi and lets divers cross through when the sea conditions allow. Middle Arch has deeper, longer swim-throughs at 19 to 23 m, and Fraggle Rock is a narrow chimney that drops to an exit at 39 m.

Northern Arch brings large shoals of fish and the chance of bigger pelagic species, while small caves hold shy, dark-loving fish such as blue moki and bigeye. Stingrays are seen here. The cliffs block access from the sea, so these are boat dives, and arches can collapse while new ones slowly form.