Bioluminescent bays or "bio bays" are bodies of water where microscopic organisms called dinoflagellates grow in quantities large enough to produce a "glow-in-the-dark" effect called bioluminescence. When you paddle or splash the water, these organisms shine in a neon blue-green color, making the water look as if it was lit by billions of glowing stars.

There are only five ecosystems in the world where the concentration of these dinoflagellates is high enough to be considered a bioluminescent bay, and Puerto Rico is home to three of them!

Did you know that Mosquito Bioluminescent Bay in Vieques, Puerto Rico is the brightest bio bay around the world? This recognition was awarded by Guinness World Records in 2006.

Puerto Rico's three bioluminescent bays are Mosquito Bay on the island of Vieques, Laguna Grande in Fajardo, and La Parguera in Lajas. Visiting a bioluminescent bay is a truly one-of-a-kind experience that you shouldn't miss in Puerto Rico. Luckily, these natural wonders are accessible from several of the most popular cities in Puerto Rico for visitors, and not far from the Port of San Juan for cruise passengers. Here's what you need to know to plan your trip!

Mosquito Bay


Recognized in 2006 by Guinness World Records as the brightest bioluminescent bay in the world, Mosquito Bay in Vieques captivates with its beauty and pristine setting. The bay's mesmerizing brightness is due to the large concentration of dinoflagellates – a quantity that was inexplicably doubled after Hurricane María – ranging from an average of 1,000,000 to 2,100,000 per gallon of water. The lack of light pollution surrounding the Natural Reserve of Mosquito Bay and the mangrove swamps that feed the plankton make this natural spectacle one of Puerto Rico's true wonders.

Getting to Vieques

To get to Mosquito Bay, you'll first need to take a short flight or ferry to Vieques. Flights take about 25 minutes and leave from Isla Grande airport in San Juan. Ferries take about 45 minutes and leave from Ceiba in east Puerto Rico.

How to Get to Vieques & Culebra

Mosquito Bay Bio Bay Tours

The bay is located on the south side of Vieques, not far from the main town of Esperanza where you'll find many of the island's hotels and guesthouses. There are several local tour companies that offer guided tours of Mosquito Bay. Most tours meet in the Esperanza town center then travel to the bay via bus or van. Oftentimes, there are multiple tour times per night – one just after sunset and one around 8 p.m. 

Mosquito Bay is accessed by kayak only. Some kayaks have glass bottoms which allow you to see the glowing water and billions of microorganisms beneath you. A tour guide will lead a small group of kayakers around the bay, pointing out features of the bay and explaining the science of bioluminescence. Most tours do not require guests to have prior kayaking experience.

Visit our Vieques page to search tour providers.

A couple kayaks through Fajardo's bioluminescent bay

The water will sparkle as you explore the uniqueness of Puerto Rico's bioluminescence. 

Laguna Grande


Laguna Grande in Fajardo is the most visited bio bay in Puerto Rico due to its proximity to San Juan. It's also the only one of the three that's not technically a bay; the long and narrow canal that leads to the dazzling “glow-in-the-dark” water makes this unique waterbody a lagoon!

Similar to Mosquito Bay, you'll find a range of kayak tour options in Laguna Grande, with many offering multiple time slots per night. 

Getting to Laguna Grande

Laguna Grande is located on the eastern tip of Puerto Rico's mainland in the town of Fajardo. From San Juan, it's just a one-hour-and-fifteen-minute drive to Laguna Grande. Since the tours take place at night, you'll probably want to spend the night in Fajardo. There is much to see and do in Puerto Rico's east region, so consider sticking around to explore Fajardo's beautiful beaches, take a catamaran boat charter to uninhabited Icacos Island, or spend a day exploring El Yunque National Forest.

Find places to stay, bio bay tour companies, and more trip ideas on our Fajardo page.

People swim in La Parguera bio bay

La Parguera is the only bio bay in Puerto Rico where swimming is allowed.

La Parguera


The bioluminescent bay at La Parguera, located in Lajas at the southwestern corner of Puerto Rico, is the only one where motorboats can come in and out. La Parguera is also the only bio bay where swimming is permitted, and some guided tours provide you with equipment so that you can dive in and swim after dark. You can also take a glass-bottom boat ride and spend the night contemplating the organisms that make the bay glow. 

Getting to La Parguera

For those staying in Rincón on their trip to Puerto Rico, La Parguera is the best bio bay to visit. It's just over one hour away by car, making it an easy day trip.

From San Juan, the drive is about two hours and fifteen minutes. There are some tour companies that provide full-day tours to La Parguera with transportation to and from San Juan, lasting about eight hours in total. 

No matter where you'll be coming from, La Parguera is a water sports paradise that you should take your time to explore. Find tour providers and accommodations on our Lajas page, or check out this Six-day La Parguera itinerary.

Hand in water at a bioluminescent bay.

Shaking up the dinoflagellate organisms in a bioluminescent bay will feel like playing with stars.

How to Best Enjoy a Tour (and What to Avoid)

While bio bays worldwide are seasonal, the bioluminescence in Puerto Rico is year-round, but there are a few things to keep in mind when planning your trip.

  • The less light, the better. To best enjoy the luminescence, try to avoid full moon nights. Note that if it is a full moon, the water will still glow, but the darker it is, the more you'll witness the effect that movement has on these single-celled organisms.
  • Tides and water temperatures affect the brightness of the bays as well. Call a day or two in advance to confirm that the bay's brightness has been above 30% in the days before your tour. 
  • Most of these eco-adventures are made in kayaks, so wear comfortable clothing for paddling. For conservation purposes, swimming at the bay and lagoon is not allowed (with the exception of La Parguera).
  • Avoid using hand creams, bug repellant, and any other lotions that can harm the organisms. 
  • Motorboats are strictly prohibited. 
  • Prices vary depending on the Bay Tour Operator (BTO), but range from $48 to $76 per person, taxes included. The Department of Natural Resources has a list of over 13 tour operators authorized to carry on guided tours
  • Tour operators typically offer two trips per day: around sunset, and a later one after 7:30 p.m. The earlier tour gives you the chance to see the mangroves and absorb the environment as you kayak toward nightfall. Later trips fully guarantee the darkness needed to see the dinoflagellates glow throughout your adventure. 
  • Taking your camera is unnecessary—it won't capture the glow as you see it. Instead, immerse yourself in the experience, don't risk getting electronics wet, and enjoy the moment.

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