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In 2013, a Guatemalan fisherman made a stunning discovery: a massive, uncharted coral reef, straddling the waters of Guatemala and Belize. He shares the secret with only a few people, including coral reef expert Ana Giró Peterson. After seeing the “mesmerizing” reef with her own eyes, Peterson and colleagues embark on a scientific journey to chronicle a tantalizing treasure that will raise hopes for the survival of coral reefs around the globe.

The Cayman Crown, as the reef is dubbed, sits atop an underwater mountain overlooking the deepest part of the Caribbean. It has the most live coral cover of any reef in the region by a wide margin. And it is rich with life. Whale sharks and eagle rays thrive alongside schools of snappers and blue tang; feather duster worms and sea fans sway in the Crown’s rich waters; and enormous barrel sponges serve as hiding places for rare Nassau groupers.

The Crown is also remarkably resilient. Elsewhere, warming waters have led to mass die-offs of coral, which happen when they eject their food-producing partners and bleach a ghostly white. After resisting multiple regional bleaching events, the Crown takes a direct hit in 2019. But—to the team’s astonishment—the reef makes an extraordinary recovery just a few months later.

Several factors may explain the Crown’s resilience. Cold, nutrient-rich waters likely well up from the depths and flow over the reef, cooling it. And just as Caribbean water temperatures are at their hottest, muddy waters from seasonal downpours sweep from the land out to the reef—possibly shielding corals from damaging sunlight. Another factor may be the corals themselves. The team finds an abundance of slow-growing corals that can withstand warming waters.

The discoveries suggest the Cayman Crown may be a heat-resistant “super reef”—a refuge that could help revive embattled reefs throughout the Caribbean. And the Crown may also offer prime spawning grounds for the critically endangered Nassau grouper. Prized by fishers, the species was once the backbone of the local economy. The researchers scour the Crown for potential grouper breeding sites; identifying these could help preserve fish populations—and the livelihoods of fishing communities. Their efforts pay off in 2020, when the governments of Guatemala and Belize commit to protecting the Crown.

The conservation win may be short-lived, however, as evidence emerges that the Crown is in peril. Two years after their victory, the researchers uncover evidence that fishers have been targeting the Crown, and they strain to find any groupers at all. Because they’ve been working with local fishing communities to preserve the reef, the researchers suspect lawbreakers from outside Belize and Guatemala. The team calls for the enforcement of no-take fishing rules and embarks on an experiment to lure groupers back to the Crown.

Securing protection for this treasure of the Caribbean has inspired the team and buoyed their spirits. But the fight for the reef’s future has only just begun.