Here, in Boat Cove, a sheltered crook of Raoul Island, a massive plate coral and other species cling to the reef. Coral is actually an assembly of smaller animals, zooxanthellae, and algae living together as a colony. In turn it supports a wider community of small fish and—lurking in the background—sharks.

The Kermadecs are not as remote as they once were. The long arms of climate change are altering sea temperatures and acidity—a particularly concerning factor in a location where coral is already on the edge of its range.