La Parguera is a bioluminescent bay found in the southern town of Lajas— a two-hour drive from San Juan. One of three bioluminescent bays found along Puerto Rico's coastline, the bay's glowing effect is made possible by micro-organisms called dinoflagellates, which emit a short burst of light when the water is agitated. Various tour companies offer nightly kayak or boat trips to explore the bay's waters. Contrary to the other two bio bays found in Puerto Rico, La Parguera is the only one where swimming in the vivid waters is allowed, so don't forget to pack your bathing suit.