On the Southern shore of Vieques Island in Puerto Rico lies Puerto Mosquito, an unassuming, calm, little bay that is beautiful, but fairly unremarkable by daylight. At night, however, millions of microorganisms called dinoflagellates turn the bay into a virtual, glowing sea of stars. These tiny creatures use light as a defense mechanism to distract potential predators, and glow a soft greenish-blue when disturbed. Every time they are touched, pressed under your footsteps in the sand, or hurtled onto the beach by a wave, the dinoglagellates light up. Each individual organism is barely visible to the naked eye, and only flashes for 1/100 of a second, but by the millions, they create sparkling, eerily beautiful, soft-glowing patterns in the water. Puerto Mosquito has the highest concentration of bioluminescent algae because of its perfect conditions. In order for this amazing display to happen, the dinoflagellates need a warm, shallow bay that is protected from the ocean’s crashing waves and currents, and rich in nutrients. There are only four other bioluminescent bays in the world: two more in Puerto Rico, one in Vietnam, and one in Maldives. Puerto Mosquito’s bay contains about 750,000 dinoflagellates per gallon of seawater, making it the brightest bioluminescent bay on Earth, and also the most visited. Because of the high tourist traffic to the area, special measures are taken to preserve this gorgeous natural resource. If you plan to visit, please do a little homework first and make sure you hire a licensed bio-bay tour guide—they have been trained in conservation to protect the dinoflagellates’ natural habitat. There are many illegal guides operating in the area that aren’t concerned with the preservation of the bay and its special inhabitants. Most hotels in the area offer a list of certified guides, but a quick internet search will also ensure that you’re choosing the right tour for you. There is no swimming allowed in the bay because insect repellent, pesticides, sun block, perfume, lotion, and other chemicals on your body might harm the little critters. It is also forbidden to throw anything in the water, even rocks or pebbles. Tour guides will lead kayak trips or cruise around with you on electric boats. Although it is tempting to take a million pictures of this beautiful and breathtaking phenomenon, they generally don’t turn out very well because the glow from the dinoflagellates is too weak for cameras to pick up. It only adds to the extraordinary splendor to have to experience this brilliant and magnificent event first hand.