Any trip to Vieques would be incomplete without a trip to the bioluminescent Mosquito Bay unless, of course, you visit during a full moon, when the ambient light diminishes the visibility of the bioluminescent organisms that light up the water.

Island Adventures (787/741-0720, biobay [at] biobay [dot] com, www.biobay.com, $25) operates a well-run tour of the bay that lasts about 2.5 hours and starts with a short bilingual lecture. Then guests are bused to Mosquito Bay, where they board an electric pontoon boat that tools around the electric-blue water. Guides are exceedingly friendly and informative. You’ll also get a lesson on the constellations. As if that weren’t enough, free pickup and drop-off service is provided along Calle Flamboyan in Esperanza.

If you want a more up-close and personal tour of the bay, Blue Caribe Kayaks (149 Calle Flamboyan, Esperanza, 787/741-2522) provides kayak tours of Mosquito Bay for $30 per person. Kayak rentals are also available for $10–15 per hour, $25–35 for four hours, and $45–55 all day. Snorkeling-equipment rentals are also available.