Deep blue waters that glow in the dark come night-time sound like something out of a fairytale.
However, that's exactly what the world's bioluminescent bays offer, and they make for a pretty spectacular sight.
The eye-catching effect is actually the result of a high concentration of plankton which, when they move, causes the waters to light up with a 'glow in the dark' effect.
It's a rare natural phenomenon, as there needs to be a particularly high concentration of plankton. For example, you need thousands just to make one gallon of water light up.
It's therefore not surprising that only a few shores around the world are subject to the incredible effect.
In fact, there are only five bioluminescent bays in the world - and they have the special effects because they each boast a concentration of millions of plankton.
Puerto Rico alone is home to three of them; the Laguna Grande, La Parguera and Mosquito Bay in Vieques.
Meanwhile Jamaica is home to the fourth, the Luminous Lagoon, which sits near the town of Falmouth, while the fifth is located in Halong Bay in Vietnam. It's worth noting that both of these tend to be popular tourist hotspots.
Out of all five, it's Puerto Rico's Mosquito Bay which is the brightest.
This is not just down to the high concentration of plankton, but also a series of preservation efforts which include banning boats and swimming in the bay (although it is possible to take kayak tours for those who do want to witness the phenomenon).
Other efforts have also included discouraging the use of hand creams, insect repellent and other lotions that could potentially damage the environment.
Mosquito Bay's impressive brightness can also be attributed to a lack of light pollution, a result of its fairly remote location. It all makes for just that extra touch of magic.
