The Andros Barrier Reef is the third-largest on Earth, running almost the length of the island before the seabed falls away into the Tongue of the Ocean, a trench more than a mile deep. It is a nursery, a storm barrier and a livelihood at once. The coral takes the energy out of a swell long before it reaches a settlement, and the fish sheltering inside it are the fish that end up on the table.

Across the Caribbean, reefs have lost most of their coral cover in a single lifetime, to warming water, to disease, and to the loss of the grazers that keep algae off the rock. We survey reef health across the shallows at fixed sites on a fixed schedule, publish what we find, and back the Bahamian divers and fishers who are already protecting them.

A reef needs its grazers as much as it needs its coral. Parrotfish and sea urchins keep algae cropped short enough that coral larvae can actually settle and take hold; where overfishing has stripped a reef of its grazers, even coral that survives a bleaching event can still lose the fight to algae within a few years.

Once a year, Nassau grouper gather by the thousand at a handful of reef drop-offs to spawn, all on the same few nights around a winter full moon. Those aggregations are easy to find and easy to net out entirely in a single season, which is exactly what happened to most of the Caribbean's; protecting the handful of sites that still hold one is protecting the species' entire future at once, not just a single reef.