The Poor Knights are a pair of volcanic islands about 23 km off the Tutukaka coast, surrounded by a 1981 marine reserve that is one of the best-known dive sites in the world. The volcanic rock has been carved by the sea into a labyrinth of caves, arches, and tunnels, including Riko Riko, claimed as the largest sea cave in the world by volume.
Underwater, the East Australian Current sweeps subtropical species south to mingle with cooler-water natives: schools of pink and blue maomao, kingfish, stingrays, and the occasional manta or mola mola. Visibility is typically 20–30 metres in summer, and the water sits around 20–22°C. Above water, the islands are a sanctuary for tuatara, Buller's shearwaters, and the giant Poor Knights lily, which flowers nowhere else. Landing is forbidden, but boats anchor alongside the cliffs and snorkellers and divers swim in directly from the surface.