Trunk Bay is named after a turtle. Danish settlers thought a leatherback resting at the surface looked like a floating steamer trunk, so the animal became the trunk turtle, and the beach it crawled up took its name. The half-mile crescent of white sand is now the signature view of Virgin Islands National Park, which exists because Laurance Rockefeller bought much of St. John and gave it to the federal government in 1956. Two low rocky cays lie a short swim offshore, cutting the lagoon into bands of turquoise and jade that trace the reef below. In the early 1960s the Park Service bolted a line of plaques onto that reef and opened the first underwater trail in the national park system — a marked snorkeling route over brain coral, sea fans and squadrons of sergeant majors, built as a lesson rather than a show.
You meet the bay from above. Northshore Road pulls back at a bend and gathers the whole thing into one frame: cays, reef shadow, sand. In the water the ripples on the bottom stay sharp ten feet down, green turtles crop the seagrass at the edges of the bay, and eagle rays cross the deeper blue past the reef. What the plaques say has changed. The Park Service replaced them in autumn 2021, and the new signs tell snorkelers outright that the reef is in trouble: the 2017 hurricanes shoved the old markers across the seabed, stony coral tissue loss disease reached these islands in 2019, and the hot summers of 2023 and 2024 bleached and killed coral. The living reef is thinner than the photographs promise. The turtles are the counterweight — hawksbills nest along this coast every summer, and in April 2022 a leatherback laid a clutch on Trunk Bay itself, the first leatherback nest recorded on St. John in years.