From Marriott Traveler

Get Lit: Where to See the Sparkle of the Caribbean’s Bioluminescent Bays

After dark in the Cayman Islands, the fairies come out. They converge on a place called Bio Bay, floating serenely in the water and only appearing if disturbed by man-made craft. Kayaks float through the water, leaving a sparkling trail of fairy dust behind them, the rowers able to momentarily infuse their skin with glitter simply by scooping up a handful of the glow-in-the-dark water.

The exact reason this occurs may be a bit more scientific than fairies, but the experience is no less magical. At Bio Bay, along with Luminous Lagoon in Jamaica, tiny underwater plankton create the sparkling effect described above. It’s a phenomenon only experienced after dark and only when the plankton in the water are disturbed, say, by a paddle, boat or body part slicing through the water.

The tiny plankton are actually called dinoflagellates, and they work like a glow stick — a chemical reaction in the dinoflagellates makes them glow a bright blue. Movement in the water triggers the reaction with a compound called luciferin.

Interestingly, the light emitted from the plankton, although seeming constant to the human eye, is actually flickering, with each flash lasting about a tenth of a second. Scientists surmise the reason behind the glowing is to either startle away predators or to attract bigger ones to eat the predators feasting on the plankton.

One of the main requirements for a bio bay to exist is a narrow entrance to the bay, which keeps the plankton from being washed back out to sea. But more importantly, there needs to be a high concentration of vitamin B-12 in the water, which the dinoflagellates need to survive. Usually that means there’s a substantial population of mangroves along the shoreline, since mangroves are an excellent source of B-12.

Travelers interested in experiencing sparkling water in a bay have a few options in the Caribbean.

Bio Bay, Grand Cayman, Cayman Islands

Start your tour at Rum Point on the north side of Grand Cayman. Multiple companies operate from this spot, offering hour-and-a-half kayak tours, boat tours with a swimming component, and even snorkeling excursions so you can see the plankton up close. Cayman Kayaks, Cayman Sea Elements, George’s Water Sports and The Sweet Spot water sports are some of the best.

Expect to spend about $55 per person. Realistically it’s not necessary to sign up for a tour if you have your own kayak or boat, but to get the best experience with the most information, you’ll want a guide. Environmentalists, go with Cayman Kayaks. The company is run by a husband and wife conservationist team, tirelessly dedicated to preserving not only the glowing waters, but the endangered mangrove population along the shore that helps the plankton survive.

Luminous Lagoon; Jamaica

This spot in Jamaica follows the shore along the Trelawny marshlands from Rock to Falmouth. In the 1700s this was one of Jamaica’s most important ports, controlling the import and export of rum, sugar and other Jamaican products. Scientists discovered the bioluminescence after the decline of the sugar trade.

Tours leave from Glistening Waters Marina and last about 45 minutes, with a chance to jump off the boat and swim in the glowing water. Tour companies like Jaital and Viator offer hotel pickup.

For a longer tour sign up with Get Your Guide — the trips are two hours and give you a free rum punch during a fire limbo show to cap off the evening. Depending on the company you decide to go with, prices range from $45 to $60.

A Note about Puerto Rico: Long considered the best and most iconic bioluminescent bays in the Caribbean, Puerto Rico’s Laguna Grande, Mosquito Bay (ranked the world’s brightest by Guinness in 2008) and La Parguera are unfortunately currently dark due to devastation from hurricanes. Scientists, though, are hopeful the bays will recover their signature glisten.