Culebra's idyllic Flamenco Beach has gorgeous views, stellar snorkeling and swimming opportunities, and iconic tanks that hark back to a time when the island was a naval base.
You can also visit the uninhabited Isla Culebrita to dive the nearby reef, search for sea turtles, and explore the seabird nesting grounds and turtle refuge.
If you're staying on Culebra, grab a dinner loaded with fresh seafood options, take a walk on uncrowded beaches, and meander around, looking for sculptures, murals, and other art.
Vieques has beaches, water activities, and the Vieques National Wildlife Refuge, which spans half the island and houses many animals in its lagoons, forests, and wetlands.
Vieques is also home to the world's brightest bioluminescent bay, which you can kayak above. The algae are brightest on a night when the moon is in a new or crescent phase.