In Puerto Rico, something odd happens at nighttime in Vieques, Mosquito Bay, the water in the bay glows. Puerto Rico has 3 bioluminescent bays, the brightest is Mosquito Bay in Vieques, the second brightest is Laguna Grande in Fajardo, and the least brightest is in La Parguera.
In the water, there are microorganisms called bioluminescent dinoflagellates, the bay glows a blueish/greenish color, when the micro-organisms are agitated. The bay contains up to 720,000 single-celled bioluminescent dinoflagellates per gallon of water. The water is a beautiful sight to see and it is a one in a life time experience and if you love swimming in the water and quiet a risk-taker, you should have a swim in the water because it is completely harmless.