US Virgin Islands

The US Virgin Islands are an archipelago of three main islands — St. Thomas, St. John, and St. Croix — and roughly 50 smaller cays, spread across the northeastern Caribbean between Puerto Rico 65 km to the west and the British Virgin Islands immediately to the east. The tidal regime is eastern Caribbean microtidal: spring range 0.2–0.4 m, mixed semidiurnal with significant diurnal inequality. St. Croix, 70 km south of St. Thomas, sits in slightly different tidal waters from the northern pair and can show a phase difference of 15–30 minutes versus Charlotte Amalie. Charlotte Amalie on St. Thomas is one of the Caribbean's busiest cruise ship ports, regularly hosting 6–8 vessels simultaneously; the harbour infrastructure is dimensioned for commercial traffic, and tidal water level is rarely a limiting constraint for vessels of any size given the shallow range. St. John is the most protected of the three: 60 percent of the island is US National Park, development is restricted, and the beaches at Trunk Bay and Cinnamon Bay draw day-trippers from St. Thomas on the 10-minute ferry. The shallow shelves and reef systems throughout the USVI mean that even the small Caribbean tidal range exposes reef crests at low water — relevant for snorkellers, kayakers, and anyone navigating a shallow-draft vessel through the inter-island passages.