I had heard how beautiful the world's brightest bioluminescent bay is (Mosquito Bay on Vieques, Puerto Rico) but I had no idea it was going to be as breathtaking as it was. I just returned from there last week. Unfortunately we didn't sail there and we didn't even get to sail any during the entire trip, but I had to share our experience because you can definitely sail there (not into the bay though since it's restricted) and for those of you who haven't seen it, add it to your bucket list!! The bioluminescent/glowing blue effect is caused by microscopic organisms named Pyrodinium bahamense, Dinoflagellates (dinos). When anything touches them or moves them they start glowing as a defense mechanism. There are billions of them in the bay. You're not allowed to swim in it any longer because it harms the environment and kills them but you can dip your hand into the water and it will leave a blue trail behind. And when you pick up your hand out of the water it will glow, and the water that drips off of it glows! We took a glass bottom kayak tour of the bay and a fish swam under our kayak for 10 or 15 minutes and you could see it perfectly because it was glowing so brightly!! You could see fish everywhere (but under the kayak through the glass bottom was unbelievable!). I can't even find the words to describe how incredible this experience was!! Unfortunately, we couldn't bring our phones on the tour with us so I didn't get pics but I'm including a pic from the tour company's website (Melaya Tours). If you get a chance to go to Puerto Rico you have to go to Vieques and see the biobay (make sure to go during a "New Moon" phase). I'm also including a screen shot of my Navionics mobile app so you can see where Vieques is in relation to the mainland and where Mosquito Bay is on Vieques.