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The Ultimate Insider's Guide to Bio Bays in Puerto Rico

As the sun sets over Puerto Rico, the twinkling lights in the island’s bioluminescent bays come to life, casting an eerie blue-green glow below the surface of the water.

If you’ve ever searched for pictures of Puerto Rico’s glowing water online, or watched the scene in “Life of Pi” when the boy dips his hand into the luminous sea beneath him, you can likely picture the glow-in-the-dark water that gives the bays their name.

To truly experience the magic for yourself, a trip to one of Puerto Rico’s bioluminescent bays is the best way to live your fantasies of floating in the sparkling blue oasis. Three otherworldly bays call the island home, their warm, inviting waters beckoning visitors from far and wide.

With three bays to choose from and many factors to consider before booking your trip, planning a visit to the bio bay requires some research, but the end result is sure to be the most magical moment of your vacation.

3 Things You Should Know About the Bio Bays in Puerto Rico

Ceratium/Dinoflagellate (Protozoa) under microscope.
Microorganisms are the cause of the famous glowing water in Mosquito Bay

If you’ve ever seen photos of a bioluminescent beach or bay, you might be wondering if all the hype is really worth it. And what makes the bay glow in the first place? Underwater lights? Magic? A trick of the moonlight? Think again.

Magic might be one way to describe it, but the Puerto Rico bio bays glow all on their own thanks to a pretty amazing biological phenomenon.

The bays’ distinctive, ethereal blue-green glow can be attributed to millions of microorganisms known as dinoflagellates. These little light-emitters make their food by photosynthesis, and it’s this process that creates the glow.

We start to see their light as the sky grows dark, but the real magic happens when these microorganisms are agitated by the stroke of a paddle in the water or fingertips trailing below the surface.

With up to one million of these single-cell organisms per gallon of water, the phenomenon has been described as a soft smattering of pixie dust floating through the water.

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There are only a handful of bioluminescent bays in the world, and Puerto Rico has 3 of them!

It should come as no surprise that bioluminescent bays are a rare occurrence and one of the world’s best kept secrets.

You’ve probably heard of Mosquito Bay, the island’s largest and most popular bio bay, but there are also La Parguera on the southwestern side of the island, and Laguna Grande to the northeast, each with their own distinct characteristics. More on these later.

The other bioluminescent bays are located in Jamaica and Vietnam, but a trip to Puerto Rico offers more choice and variety in bio bay activities.

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Bio bays might not be around forever, so you should visit them while you can!

Venice is sinking. The Taj Mahal is close to collapsing. And the world’s small handful of bioluminescent bays, like the three found in Puerto Rico, are on the verge of permanently going dark.

A wide range of environmental factors, like pollution, wind and rain, and presence of mangroves, affect the bays’ glow factor. When Hurricane Maria struck Puerto Rico 2017, it was as if someone flipped a light switch at Mosquito Bay – the water had gone dark.

An excess of rain, high winds that push the dinos out to sea, and damage to the mangroves – which provide an essential vitamin to the organisms – were to blame. And although the glow restored itself over the following months, Mosquito Bay and bioluminescent bays all over the world just aren’t as bright as they used to be.

As factors like pollution and natural disasters change the delicate chemistry of the world’s bioluminescent bays, there’s no telling how bright the bodies of water will glow in the years to come, making Puerto Rico’s bio bays must-visit destinations during your next trip.

Which of Puerto Rico’s Bio Bays is really worth a visit?

The short answer? All of them – depending on how much time you have, where you’re staying, and what type of tours you want to do. Choosing between the three bays can be a little tricky, but with these tips, you can cross that dream tour off your bucket list with ease.

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Mosquito Bay

If you’ve paid any attention to Instagram or social media in general while planning your Puerto Rico trip, you’ve likely seen photos of Mosquito Bay, the largest and most impressive of the island’s bio bays. This bay holds the Guinness World Record as the brightest bio bay in the world, owing to the largest concentration of dinoflagellates and a helpful lack of light pollution that makes the tiny fairy lights stand out even more.

Location: Vieques Island, off the east coast of Puerto Rico.

How to get there: Vieques really is a bucket-list destination – and that means putting in a little more effort to get there. Trust us, it’s worth it! 

Travel to Vieques one of two ways: Take the ferry or fly. A 25-minute flight from San Juan International Airport (SJU) is convenient and priced very reasonably if you book well enough in advance. The alternative, a ferry trip from Fajardo or Ceiba, requires a 1.5-hour drive from San Juan (if you don’t have your own vehicle, shared transportation could take up to 4 hours!) and about 45 minutes on the ferry. While the ferry costs less than $5 roundtrip, you might want to save yourself the trouble and take the plane. Plus, the views are out of this world!

Pros: 

  • Brightest bio bay with the least amount of light pollution
  • Beautiful mangroves and wildlife can be seen from your kayak

Cons:

  • Requires more travel time (and an overnight stay since your tour takes place at night)
  • No swimming
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Laguna Grande, Fajardo

Since you’re likely flying into San Juan, the Laguna Grande bioluminescent bay in Fajardo is an excellent option for those who want to stay near the metro area. Just a short drive from the city, Laguna Grande is the brightest bio bay on the mainland. Although light pollution from nearby towns is present, a trip to the bioluminescent bay in Fajardo is an unforgettable experience with a unique twist – the so-called bay is actually a lagoon! Your kayak tour puts in at the mouth of a long canal that leads to the lagoon, where the light show begins.

Location: The northeast tip of the island, just 45 minutes from the San Juan metro area.

How to get there: Rent a car or hire a taxi or shuttle service for the quick drive, as public transportation options can take multiple hours with several stops.

Pros:

  • Conveniently located to San Juan
  • Canal and lagoon make for a unique experience

Cons:

  • More crowded due to proximity to San Juan
  • More light pollution
  • No swimming
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La Parguera, Lajas

You may have heard that La Parguera is the smallest and least bright of Puerto Rico’s bio bays, but that doesn’t mean you should cross it off your list. If you’re staying in Lajas or the surrounding area, La Parguera offers a chance to see the bioluminescence without traveling far. While it isn’t the best example of a bio bay, it’s still better than not seeing one at all. As a bonus, because this bay is the least visited, tours are often less expensive and easier to book. Also, snorkeling or swimming may be an option depending on the tour operator.

Location: Lajas, southwest side of the island. 2 hours from San Juan.

How to get there: Renting a car is best.

Pros:

  • Least visited bio bay = less expensive
  • Swimming may be allowed depending on the tour company

Cons:

  • Darkest bio bay
  • Not as well preserved as the others due to over-boating
  • Far from San Juan

4 Things to Keep in Mind Before You Book Your Trip

If you’ve determined which bay you want to visit, you’re ready to book your Puerto Rico bioluminescent bay tour. Check out these tips for the best experience possible.

Phases of the moon from new to full
Plan your trip around the lunar cycle

That’s right, it’s time to break out your lunar calendar!

Even if you’re visiting Mosquito Bay, the brightest of Puerto Rico’s three bio bays, the light of the moon can still make or break your experience.

Try to plan your tour during a new moon, when the moon is the darkest in the sky. The light emitted close to or during a full moon can significantly dim the glow of the dinoflagellates and you might be disappointed if the effect isn’t as bright as you imagined.

Booking a tour two or three days on either side of the new moon will ensure you see the bays at their brightest.

By the way, tides and water temperature can affect the brightness of the bay as well. It’s always a good idea to call your tour operator a few days in advance to confirm that the bay’s brightness has been above 30% in the days leading up to your trip.

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Leave the camera at home

You might think it sounds crazy, but cameras just don’t do the bioluminescence justice – in fact, they won’t even capture the light in most cases.

You’ve likely seen amazing photos of Puerto Rico’s glowing beaches online and want to capture the images for yourself, but those coveted pics are often taken with professional cameras and even edited after the fact to enhance the glowing effect.

Consider your bio bay tour a chance to live in the moment and immerse yourself in the incredible natural phenomenon you are experiencing. After all, how many times during your life will you find yourself floating among millions of sparkling organisms?

Don’t risk getting your phone or camera wet. Leave it in your bag and create memories in real time.

Mosquito_bay_Bioluminescent_bay_Vieques_-_panoramio_1-1
Bio bays might not be around forever, so you should visit them while you can!

Venice is sinking. The Taj Mahal is close to collapsing. And the world’s small handful of bioluminescent bays, like the three found in Puerto Rico, are on the verge of permanently going dark.

A wide range of environmental factors, like pollution, wind and rain, and presence of mangroves, affect the bays’ glow factor. When Hurricane Maria struck Puerto Rico 2017, it was as if someone flipped a light switch at Mosquito Bay – the water had gone dark.

An excess of rain, high winds that push the dinos out to sea, and damage to the mangroves – which provide an essential vitamin to the organisms – were to blame. And although the glow restored itself over the following months, Mosquito Bay and bioluminescent bays all over the world just aren’t as bright as they used to be.

As factors like pollution and natural disasters change the delicate chemistry of the world’s bioluminescent bays, there’s no telling how bright the bodies of water will glow in the years to come, making Puerto Rico’s bio bays must-visit destinations during your next trip.

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Bio bay tours sell out fast so book your tour as soon as possible

If you’re one of those spontaneous travelers who loves booking trips at the last minute, you might want to reconsider.

Due to the high demand for bio bay kayaking tours and the likelihood of everyone trying to schedule tours as close to the new moon as possible, you need to plan your bio bay tour as soon as you decide to travel to Puerto Rico.

With some companies booking a full year in advance, there are no excuses for missing your chance to visit one of Puerto Rico’s bio bays! You could probably put off booking your flight for a few days, but whatever you do, don’t forget to book your Puerto Rico bio bay tour! You’ll thank us later.

Book Your Bio Bay Tour Online

Ready to take the plunge? A visit to one of the island’s bio bays is an absolute must during your Puerto Rico vacation. With so many tour operators to choose from, your trip can be exactly what you want it to be. Peer into the depths through a glass-bottom kayak, float in the light of La Parguera, or stir up the water with your hands and feet to get those dinos moving!

Check out these tour operators for an unforgettable tour of Puerto Rico’s bio bays