Bioluminescent dinoflagellates © Hans Hillewaert
When disturbed, the waters of Mosquito Bay sparkle like a starry sky due to the massive concentration of bioluminescent plankton living beneath the surface. Vieques's Puerto Mosquito holds the Guinness World Record as the brightest of similar bays found elsewhere on the plane. A trip to Bio Bay, as it's locally known, is one of the best tourist attractions in Puerto Rico and well worth the excursion from San Juan. Several tour companies offer kayaking and snorkelling in the magical water, creating a genuinely dreamy environment of ethereal romance. The bioluminescence is at its brightest during the full or near-full moon, and this is considered the best time to visit.