The bioluminescent bays in Puerto Rico emit a blue light when you touch the water. This is due to the billions of dinoflagellates living in the water, which think they are under attack and try to glow to defend themselves from us, the predators. This has a very cool effect when you go swimming, and it makes it seem like you and the water are glowing light blue. There are 5 known bays in the world, and Puerto Rico is home to 3. The 3 bays are the  Mosquito Bay, Laguna Grande, and the La Parguera. The other 2 are in Vietnam and Jamaica. While Hurricane Maria destroyed a lot of the mangrove forest, many of the mangroves still stand, and people marvel over them every day. You can take kayaking tours into the bays, but motorboats are not allowed in the water because they could destroy the organisms in the water, which would make it less cool when others come to visit. One of the bays even lets you swim in it, giving you a whole new experience.