When thinking of cruising or chartering in the Caribbean, many sailors think first of the British Virgin Islands, perhaps because so many charter companies are located there and eventually everyone knows someone who has chartered in the BVIs. But for those who prefer to get off the beaten path and see more than just other boaters and facilities (and bars) created for charterers, the US Virgin Islands have much to offer - and St. John especially is spectacular and shouldn't be missed. Indeed, some savvy bareboaters head to St. John immediately from a charter base in Tortola or elsewhere rather than sticking to traditional, and often more crowded, BVI cruising grounds.
As in much of the Caribbean, the climate of the US Virgin Islands is about as perfect as it gets and varies little throughout the year. Winters, expect lows around 70 or above, highs in the low 80s. At the height of summer, expect lows in mid to upper 70s and highs in upper 80s. September through November is the rainiest period, although even then showers are usually brief and occur most often in the morning or at night. Day-long storms and multiple days of rain are rare.
The sailing is spectacular throughout the Virgin Islands, which generally experience steady eastern trade winds year-round. The islands are fairly close together, so even if you're beating into the wind to head east, you're not doing it for terribly long. The water between the islands is deep and the charts well marked, making most navigation simple and straightforward. And there are dozens and dozens of places to go.
Anchorages/Moorings. Most cruisers and charterers tend to anchor or pick up moorings in the Virgins, in part because there are relatively few marinas but mostly because there are so many beautiful and accessible bays, coves, and beaches to experience. St. John is by far the best area to explore, given its beauty and many accessible anchorages away from towns and tourists. Spend some time studying maps and charts before you go, and pick up a copy of Gerald Singer's great little book St. John Off the Beaten Path, which describes bays, beaches, coral reefs, trails, and other helpful land characteristics.
NOAA makes available free charts for the US Virgins, which you can load into your laptop's chartplotter, such as the excellent free Open CPN - or use a navigation app on your smart device. Most charter companies will provide the charts and likely a chartplotter, of course, but it's fun to study these on your own before sailing in. Pay close attention to restrictions on anchoring, such as in many areas of the National Park waters around St. John where anchoring is prohibited because of the risk of damaging coral. Moorings are available in many of these areas for a low fee, however, allowing you to swim or dinghy ashore or to snorkel the reef directly from your boat.
Most bays cut deep into the mountainous shoreline and provide good protection from the prevailing easterlies. On a rare northerly blow, you can tuck in deeper in waters such as Francis Bay on St. John's north side (protected by the Mary Point headland) or swing around to bays on the south side of the island.
In addition to charts, I'd recommend ordering the National Geographic outdoor recreation map of the Virgin islands (St. John), which clearly shows the location of coral reefs, trails, and other natural features to help you plan your days.
Marinas/Charters. Red Hook on St. Thomas is the location of sail charter companies. It's only a short hop from there to St. John and nearby cruising grounds. More charter companies are located on Tortola in the BVIs, also nearby but a little more expensive to reach from the US mainland.
Snorkeling and Diving. The snorkeling is so good all around St. John that it's difficult to recommend less than a dozen places. The Off the Beaten Path book referenced above devotes many chapters to describing the different species of coral and fish, turtles and rays, and other underwater life found in abundance. My personal favorites are Leinster Bay (around Waterlemon Cay) on the north side of St. John or the east side of Secret Harbor on the southeast side of St. Thomas.
Many of the reefs are just below the surface, so you don't need to dive to see lots of fish, turtles, rays, and hard and soft coral. Most plentiful are parrotfish of every color, snappers, butterfly fish, grunts, angelfish, and dozens more - along with spiny urchins, elkhorn coral, brain coral, soft corals, and purple sea fans.
There are dive shops in Red Hook, St. Thomas, and Cruz Bay, St. John, for those wanting to venture deeper or offshore. If you have your own gear, they'll direct you to the best places.
Of the three large US Virgins, St. Thomas is the most touristy and is ringed by resort hotels and condos. The one city of size, Charlotte Amalie, the location of the international airport, is visited almost daily by cruise ships, whose shoppers descend upon the hundred shops downtown, which then mostly close when the cruise tourists depart. The harbor is large, open, and easy to enter, making this a good landfall for those sailing down from the US and elsewhere, but otherwise this area has little to interest most cruising sailors who are likely trying to get away from such things. At the far east end of St. Thomas, the town of Red Hook is the island's sailing center, hosting several marinas, charter operations, and chandleries for those needing to reequip or make repairs - and of course the requisite sailors' bars.
The island of St. John, a stone's throw east of St. Thomas and just southwest of Tortola in the BVIs, is at the other extreme and is a delightful cruising paradise. Most of the island and its waters lie within the Virgin Islands National Park, which protects not only the land and beaches but also the coral reefs. The snorkeling is excellent in many areas and easily accessible from beautiful white sand beaches and boat moorings. Only a few hotel resorts take up space on St. John, such that most of the island is pristine and undeveloped. Most shoreside activities involve an appreciation of nature. There are good hiking trails all over, and many beaches and coves are virtually empty of people. Tourists coming over for the day from St. Thomas rent jeeps to traverse the island or ride in large open-air sightseeing taxis to a few popular spots, such as Trunk Bay on the north side, while other bays and beaches that can be reached only by hiking or boat will feel like your own private place: Francis Bay, Leinster Bay, and Brown Bay on the north, for example, or Saltpond Bay and Great Lameshur Bay on the south. Dinghy in to Cinnamon Bay Campground for provisions at the camp store or to rent a kayak or paddleboard.
Cruz Bay on the west end is the ferry port and St. John's only town of size; here you can find provisions and restaurants and gift shops. On the east end is the hamlet of Coral Bay, where there are a few funky pubs and shops for the hardier types who make it across the island or who sailed into Hurricane Hole and never left. Check out Skinny Legs "a pretty OK place" bar and restaurant for a taste of local color.