Glowing blue water in a bioluminescent bay

Bioluminescent Bays in Puerto Rico

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Published: October 12, 2019 • Updated: September 19, 2022 • 5 min read


On your search for things to do in Puerto Rico, you might have already read about the bioluminescent bays (bio bays). They make for a truly unique and unforgettable experience — one you can’t miss out on. The great thing about it, it’s an activity that’s accessible after dark. It’s meant for all types of travelers, nature lovers, and families alike.

Where can you find the bio bays and when is the best time to see them? Here’s what you need to know before planning a tour at one of the three bio bays on the island.

What are bioluminescent dinoflagellates?

Before planning your tour, it’s good to know a little bit of background on dinoflagellates. Dinoflagellates are unicellular organisms that light up like glow in the dark stars and cause the effect we call bioluminescence. They are incredibly tiny marine organisms, but sometimes they’re found in freshwater as well. It’s a type of plankton, and usually harmless for humans to be in contact with. An exception to this would be an overpopulation of certain types that cause ‘red tides.’

The dinoflagellates in the bio bays we’re talking about are harmless. The moment something gets in touch with them, they light up for a second. These white firefly-like lights you can then see is caused by the chemical reaction that happens upon contact.

This effect is why swimming or playing around in the water with bioluminescent dinoflagellates is such a cool experience. You can literally ‘throw’ glistening water up in the air and for a split second witness being surrounded by the tiniest stars.

Exploring Puerto Rico’s bioluminescent bays


Mosquito Bay, Vieques Island

To see the bioluminescence at Mosquito Bay, you’d have to fly or ferry over for at least an overnight trip to the small island called Vieques. It’s just east of the island of Puerto Rico. Mosquito Bay is the biggest and also said to be the brightest bio bay in the world (Guinness Book of World Records, 2006).

After Hurricane Maria in 2017, for a moment, it looked like there was a setback for Mosquito Bay. But by 2019, the brightness is double than it was before. This is due to the relocation of dinoflagellate colonies after the hurricane.

At Mosquito Bay, you can take an electric boat or glass-bottom kayak tour, that allows for a very close-up magical experience while staying dry yourself. The 2-hour guided kayak tours start at around $60.


La Parguera, Lajas

Near the southwest corner of Puerto Rico, and a 3-hour drive from San Juan, there is the bio bay of La Parguera. Right at the lively little town center of La Parguera in Lajas, motorboats depart after dark (starting 7:30 pm) to the nearby bioluminescent bay. You can’t miss the vendors near the dock, and it’s very easy to get a ticket for this experience.

Prices for a 30-minute tour start as low as $10. Bring your swimsuit, as this tour allows for swimming unless the weather is unpredictable. On the way back, you can see the lights of the town and the scenic wooden fisherman’s houses right at the waterside with their boats docked out front.


Laguna Grande, Fajard

A one hour drive from San Juan to the east coast of the island brings you to the town of Fajardo. There you can see the bioluminescent bay of Laguna Grande. For Laguna Grande, the best and most common way to see the bioluminescence is by one of the kayak tours that start at sunset and have you paddling into the dark to see the phenomenon.

The other options include a walking tour and an electric boat tour. In this bio, bay swimming is not allowed to protect the health and ecosystem of the bio bay. Kayaking tours will take around two hours total, and they leave from Las Croabas in Fajardo. The average price for this tour is $60.

4 tips for a next-level bioluminescent bay experience

  1. Plan your trip around a new moon. A quick Google search will tell you when that is. You’d want to go when it’s as dark as possible out. Or, in other words, with the least amount of light pollution. Around the new moon, there’s hardly any moonlight, and that makes the bioluminescence even more visible. If you go during a full moon, the moonlight will dim the organisms.
  2. Look up as much as you look down to the water. In dark places like these, when the sky is clear, there’s usually an impressive amount of stars visible in the air. While on your boat or kayak ride, you should watch the stars in the endless sky — it’s unreal. Especially if you’re a city-dweller, this is something you won’t often see where you live.
  3. Don’t do it for the ‘gram. Forget about taking pictures or videos, as they won’t turn out the way you want to. Far from that: most likely, your shots will be all black, unless you carry highly professional equipment (and skills) with you. Instead, use your time on the water to be in the moment and enjoy it. You will be in an out-of-this-world type of environment.
  4. Be an environmental-friendly human. When you plan on swimming, try not to wear any creams or make-up as the chemicals can end up in the water and slowly but surely this is damaging this beautiful ecosystem. Biodegradable bug repellent might come in handy.

Now you’re ready to plan and book a tour in one the bioluminescent bays of Puerto Rico.

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