B366R1 The sun setting over the Puerto Mosquito mangrove bay in Vieques, Puerto Rico. The bay is bioluminescent.. Image shot 2007. Exact date unknown.
Bahía Mosquito

John MacIlwinen/Alamy

Bahía Mosquito

Top choice in Vieques

Locals claim that the magnificent Bahía Mosquito (Mosquito Bay), a designated wildlife preserve located on the island of Vieques, about 2 miles east of the town of Esperanza, has the highest concentration of phosphorescent dinoflagellates (algae) not only in Puerto Rico, but in the world.

When movement disturbs these creatures, a chemical reaction takes place in their little bodies that makes a flash, a trait scientists speculate that dynoflagellates have developed to ward off predators. As such, a trip through the lagoon is nothing short of psychedelic, with the movement of your kayak, paddle, electric boat, even fish, whipping up fluorescent-blue sparkles below the surface.

Touring the Bahía Mosquito (Mosquito Bay)

You can drive east on the rough Sun Bay road from Esperanza and stop for a view (parking well back from the water and mangroves). However, an organized trip will give you far more opportunity to really take in the spread of phosphorescence. Guides offer a wealth of information on the phenomenon as well as the flora and fauna. Look for birds including pelicans, frigate and cuckoos. In the waters below, small sharks and rays are among the fish stirring up the light show. 

Abe's Snorkeling & Bio-Bay Tours and Aqua Sunset Tours – the latter offering trips in a crystal-clear canoe, which makes an already magical experience extra-special – are two good outfits. Ensure to book tours with operators who only use kayaks or electric motors, as anything else will damage the bay's fragile ecosystem. Reservations for tours are essential in high season, and the best time to go is at new moon.

There’s another inlet to the east, Barracuda Bay, that’s also filled with dinoflagellates, but tour operators don’t venture out that far. Swimming in the Bahía Mosquito is illegal.

Hotels near Bahía Mosquito (Mosquito Bay)

The island of Vieques has plenty of accommodation options for travellers. For Bahía Mosquito, the town of Esperanza, just 2 miles to the west, makes for a great base, which boasts boutique hotels in the hills and guesthouses lining oceanfront Calle Flamboyan. For proximity to the Bay, Acacia Guesthouse and El Blok are two good options, both a 40-minute walk (or 7-minute taxi ride) away. Those counting the cents might alternatively consider Bananas, Esperanza’s original budget guesthouse.

Lonely Planet's must-see attractions

Nearby Vieques attractions

1. Playas Media Luna & Navio

0.81 MILES

If it's isolation you’re after, head east on the sandy road that runs along Sun Bay and you’ll enter a low forest. Go left at the fork in the road. In a…

2. Sun Bay

1.02 MILES

Part of Puerto Rico's national park system, this half-moon-shaped bay, less than a half-mile east of Esperanza, is the island’s balneario (public beach),…

3. Vieques National Wildlife Refuge

1.45 MILES

Lying within these protected confines are the best reasons to visit Vieques. This 18,000-acre refuge occupies the land formerly used by the US military…

5. Cayo de Tierra

1.65 MILES

A teardrop of land between the malecón and Sun Bay reached by a slender sandspit (or by wading, if storms have washed it out), Cayo de Tierra has a few…

6. Playa Esperanza

1.84 MILES

This slender beach runs the length of Esperanza. Its advantages are its spectacular views and the fact it's within shouting distance of the town’s hopping…

8. Cayo Afuera

2.01 MILES

This uninhabited pinprick of land lies a few hundred feet across the bay from Playa Esperanza. Part of the Mosquito Bay Reserve, many intrepid locals swim…