During the day, Laguna Grande in Fajardo looks like other bays along the tropical Puerto Rican coastline. But come nightfall the bioluminescent lagoon glows fluorescent, thanks to pyrodinium bahamense, microscopic plankton that thrive in its shallow Caribbean waters and glow when disturbed.
Visitors can set the water aglow and create a trail of light with every stroke of their paddles during guided nighttime kayaking tours. Trips are usually offered around the cycles of the moon, timed to the darkest nights. Some tours also combine kayaking with an afternoon nature walk to La Mina Falls in the nearby El Yunque National Forest.
There are only a handful of places in the world where bioluminescent plankton is consistently found, three of which are in Puerto Rico. In addition to Lagunda Grande, this natural phenomenon exists in Mosquito Bay on Vieques Island and the bay at La Parguera. Laguna Grande in Fajardo is surrounded by red mangrove trees, which are native to the surrounding El Yunque rain forest and provide vitamin B12 to the marine plankton.
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Kayak tours typically navigate through a tunnel of mangrove trees before reaching the glowing waters.
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Swimming in the bay is not allowed; you can swim and snorkel in the bay at La Parguera.
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Guides will sometimes bring a cover so that the tour group can observe the bioluminescence in complete darkness without starlight.
Laguna Grande is located in the Las Cabezas de San Juan Nature Reserve, just off the shores of Fajardo, about 40 miles (65 kilometers) or an hour’s drive east of Old San Juan. Tours typically depart from San Juan or Luquillo, which is 9 miles (15 kilometers) away.
Kayaking trips frequently set out in the early evening around sunset, launching from Las Cabezas with a tour guide or instructor. The best time to experience the bioluminescent bay is when the sky is especially dark due to little or no moonlight, so try to book your tour around a new moon and avoid days surrounding a full moon.
Sometimes coupled with a tour of the bioluminescent bay, a visit to El Yunque Rain Forest is a must-do for nature lovers visiting Puerto Rico. It is the only tropical rain forest in the United States Forest Service and features well-defined walking trails, lush landscapes, and plenty of wildlife such as the Puerto Rican parrot and the Coqui frog.
No, unfortunately, you can’t swim in Laguna Grande during your visit or tour. Swimming is prohibited to keep the bay at its healthiest. The only bioluminescent bay in Puerto Rico that you can swim in is La Parguera, which is a 2.5-hour car drive from Laguna Grande.
The bioluminescence bay of Laguna Grande glows with a blueish coloring because of the dinoflagellates in the water. A dinoflagellate is a microscopic organism that uses glowing as a defense when they notice any movement in the water. These short bursts of blue light have drawn tourists to the bays for years.
Yes, you can go to Laguna Grande bio bay without a tour, and it’s legal to go on the water by yourself without a guide. If it’s your first time at the bay, you may want to first plan a daytime visit to familiarize yourself with the surroundings.
The best time of night to see the effects of the dinoflagellate’s bioluminescence on Laguna Grande is at least two hours after the sun has set when the sky is dark. One of the best times is also during the new moon phase because there won’t be moonlight reflecting onto the water.
