Quick clarification we see a lot: the US Virgin Islands do not have bioluminescent bays. Those are in Puerto Rico (Fajardo, Vieques, La Parguera). Different islands, different territory.
But USVI has its own after-dark appeal. Here's what's actually worth doing when the sun goes down.
Several operators on St. Thomas and St. Croix offer night dives and snorkel trips. You'll see octopus, lobster, and reef fish that hide during the day. Buck Island off St. Croix is particularly good for this.
This is where USVI shines. Dozens of catamaran and sailboat operators run sunset cruises—most include drinks and some include dinner. The views across the harbor as the sun drops behind the islands are legitimately spectacular.
Less light pollution than Puerto Rico or Hawaii. St. John in particular has dark skies—Virgin Islands National Park covers most of the island. No formal stargazing tours that we know of, but the beaches at night are worth it.
A few operators offer LED-lit kayak tours in calm bays. Not bioluminescence—just a fun way to see the water at night with underwater lights on your kayak.
Browse 600+ USVI tours → wanderusvi.com
Filter by activity type to find sunset sails, night snorkels, and more.
Fly to Puerto Rico. It's a short flight from St. Thomas to San Juan, and from there you can reach Fajardo (1 hour drive) or Vieques (ferry or puddle jumper). We have a separate site for that: wanderpuertorico.com/bio-bay
Some people combine USVI + PR in one trip. Different vibe—USVI is quieter and more beach-focused, PR has more nightlife and activities. Both worth doing.