Trunk Bay is a half-mile crescent of white sand on the north shore of St John, in the U.S. Virgin Islands, inside the Virgin Islands national park, with two green cays offshore and the first underwater trail in the American park system laid across its reef, a line of plaques bolted to the coral that is read on a held breath, over a reef that is struggling and being treated with antibiotics. The beach was handed to the park in 1956 with most of the island by Laurance Rockefeller, which is why the north shore has no hotels, and the bay is the most photographed in the territory, seen whole from the high bend on Northshore Road on the drive in, before the queue at the beach gate below; the sand curves between two headlands with a lifeguard stand and sea grape for shade, and the water is so clear that the ripples on the bottom stay in focus ten feet down, paddled over by kayak on the line between the two cays. The snorkel trail runs out from the beach to Trunk Cay in water a few metres deep, and beyond it the seagrass holds the turtles.
The reef is sick. Stony coral tissue loss disease has moved through the Caribbean since 2014, and divers here fight it the way a doctor treats an infection, smearing a paste laced with amoxicillin onto the white lesions eating across a colony, while the territory bans the sale, the possession and even the use of sunscreen containing the chemicals that harm coral. Hawksbill turtles haul up onto the north-shore sand from June, peaking from August to November, each female returning to the beach where she hatched to lay three to five clutches a season, about 130 eggs at a time, and 37 of the island's record 44 nests in 2025 were hawksbill. The cruise crowd from St Thomas arrives mid-morning and leaves by three, when the beach empties. Trunk Bay is a beach with its reef signposted, and the signs now mark what is being saved.