Locals claim that this magnificent bay, a designated wildlife preserve about 2 miles east of Esperanza, has the highest concentration of phosphorescent dinoflagellates not only in Puerto Rico, but in the world. A trip through the lagoon – take a tour – is nothing short of psychedelic, with hundreds of fish whipping up fluorescent-blue sparkles below the surface as your kayak or electric boat passes by (no gas-powered boats are permitted – the engine pollution kills the organisms that create the phosphorescence).
You can drive east on the rough Sun Bay road 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.
There’s another inlet to the east, Barracuda Bay, that’s also filled with dinoflagellates, but tour operators don’t venture out that far.
Reservations are essential for boat and kayak tours in high season. Note that trips are often cancelled if there's a full moon or if the waters are rough.