Buck Island Reef snorkel trip

Buck Island is a dry, forested, uninhabited island of 176 acres about a mile and a half off St. Croix's north-east coast, and it and the water around it make up a national monument. You can only get there on one of the park's licensed boats, which leave from the Christiansted waterfront and Green Cay Marina. Elkhorn coral barrier reef rings two thirds of the island.

The snorkel that matters is the underwater trail at the eastern end, one of only three in the country. Guides take swimmers through in groups of six, over coral grottoes no deeper than 12 feet, with plaques on the bottom naming what you see. Beginners get a short lesson from the crew first, and non-swimmers are taken too. Most boats also stop at Turtle Beach on the island's west end for swimming and sand. Spotted eagle rays and nurse sharks live on the reef.

Half-day boats take about three and a half hours. The full-day sails run around six, with lunch and more time on the island, which leaves room for the marked trail over the crest to a lookout above the reef (45 minutes, fairly strenuous, so wear shoes and carry water). Nothing may be taken from the monument, reef-safe sunscreen or a rash guard is asked for, and the island closes at night for nesting turtles.