The Poor Knights are two main islands and several stacks lying 23 kilometres off the Tutukaka coast, protected as a marine reserve since 1981 with no public landing allowed. The volcanic islands rise sheer from deep water, and their cliffs are riddled with sea caves — including Riko Riko, claimed as the world's largest sea cave by volume.
Day trips from Tutukaka offer diving, snorkelling, and boat tours that nose into the caves. The subtropical East Auckland Current brings species not normally found this far south — bronze whaler sharks, manta rays in season, and great schools of demoiselles and trevally. Visibility regularly exceeds 30 metres. The cliffs above water host the largest colony of Buller's shearwaters in the world; they return at dusk in clouds.