How to See Bioluminescence in San Juan, Puerto Rico
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Last updated on June 26, 2025
When we booked our trip to San Juan, Puerto Rico the top thing on my bucket list was to visit one of Puerto Rico’s bioluminescent bays. Who wouldn’t want to paddle through a sea of glowing water?
We previously saw bioluminescence on a trip to Mexico, so we knew how magical it could be. But Puerto Rico is special because it’s one of the few places in the world you can see bioluminescence year-round. On top of that, it’s home to not just one bioluminescent bay, but three including one of the darkest and the world’s brightest bio bays. 😲
Naturally, that led me down a research rabbit hole to figure out the best way to see bioluminescence in San Juan. Puerto Rico’s bioluminescent bays are a fair distance from San Juan and require prep work and planning for a successful trip.
Which is precisely why I’m writing this post – to help you understand your options for seeing bioluminescence in San Juan Puerto Rico including which is the closest bioluminescent bay to San Juan and what to expect on a Puerto Rico bioluminescent bay kayaking tour.
Let’s dive in!
Table of Contents
Puerto Rico Bioluminescent Bay Map
There are 3 bioluminescent bays in Puerto Rico. However, since this post is about how to see bioluminescence in San Juan, we’ll talk about the easiest bay to access from the city, Laguna Grande in Fajardo.
Fajardo is also where El Yunque Rainforest is located. Some people chose to stay in Fajardo to visit both sites easily, but we opted for day trips since it was just over an hour to get there one way.
Top 3 hotels near Fajardo, Puerto Rico
- Wyndham Grand Rio Mar ⭐⭐⭐⭐, 8.7 rating
- Mata e’ Platano Guesthouse ⭐⭐⭐⭐, New
- Waterfront Studio ⭐⭐⭐, 9.6 rating
Explore all hotels >
Our bio bay kayak tours included transportation to and from San Juan with multiple pick-up hotels in the city. You can book the exact tour we took, which included round-trip transportation from San Juan below.
Mosquito Bay on Vieques Island is the largest and darkest of Puerto Rico’s bio bays. However, it takes the most work to get there.
You need to coordinate a rental car or Uber ride (around $80 one way) from San Juan to Ceiba. Then, get on a two-hour passenger ferry ride (ticket pre-purchase required) and get a taxi or another rental car on the island. The ferry stops at dark, so you will need a hotel on Vieques, too.
Top 3 hotels on Vieques, Puerto Rico
- Puertas ⭐⭐⭐⭐⭐, 9.1 rating
- The Vieques Guesthouse ⭐⭐⭐, 9.4 rating
- Esperanza Inn ⭐⭐⭐, 9.5 rating
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We tried to visit Vieques on our trip but realized the coordination and the short time we had in Puerto Rico, wasn’t worth it. If you want ease, Laguna Grande in Fajardo is the way to go.
Another option is La Parguera, about a 2 to 2-and-a-half-hour drive from San Juan. However, its difference makes this a less ideal bioluminescent bay to visit from San Juan.
When Can You See Bioluminescence in Puerto Rico?
Puerto Rico is one of four islands in the Caribbean where you can see bioluminescence all year. But just because they are there year-round doesn’t mean you can see them no matter when you are visiting.
🌑 Darkness is key in seeing the bioluminescence, so the best time to see bioluminescence in Puerto Rico is on a new moon. Check the moon cycles before your visit to hopefully time this experience with the darkest night.
Laguna Grande in Fajardo doesn’t allow kayak tours to visit the bay during full moons because of low visibility. If you’re visiting San Juan during a full moon, sadly you’ll have to do this experience another time.
What is bioluminescence?
Bioluminescence is not a living thing, but a chemical reaction of a living organism called chemiluminescence. Chemiluminescence creates light and is the same reaction fireflies, jellyfish and other organisms use to protect themselves or communicate with their species.
In the case of the bioluminescence in Puerto Rico’s bays, the organism is a microscopic plankton called dinoflagellates. Dinoflagellates require a very delicate balance of water temperature, nutrients, and healthy water to thrive. Puerto Rico’s three bio bays have just the right mix of each which is why you can find these tiny creatures here all year.
What to expect in Puerto Rico’s bioluminescent bays
Most photos of bioluminescence show small glowing blue algae washed up on the shores like diamonds (below). You may also see pictures where the water appears to be glowing from the depths below (above). I hate to be the bearer of bad news, but this is not what it looks like.
🌟 The bioluminescence in Puerto Rico does not look like these pictures, but is still magical!
Bioluminescence, which is the glowing effect, is activated when the plankton are agitated. That means you need to move a paddle, body, or other object in the water to activate the magical glow. You will see the water glow while you’re there, but it isn’t happening without something moving in the water, and will not be glowing constantly.
📷 Also, don’t expect to take great photos like you see here. The few bioluminescent pictures are all stock images, aside from a few paddling photos we took before it got too dark. The photographers used specific equipment and long exposure to capture the perfect blue glow. Your cell phone, or even a professional camera will not be able to mimic this (trust us we tried).
It’s still absolutely magical and you will see loads of glowing water when you move your hand, foot, paddle, or kayak. We even saw fish glowing in the water as they swam through the shallow waters of the canal! At times it felt like we were in a scene from Avatar.
The best bioluminescent tour from San Juan
There are loads of bioluminescent tours from San Juan. However, we booked our tour with GetYourGuide. We loved that this tour conveniently picked us up and dropped us off at our hotel. It also included the required life vests, kayaks, and helpful guides to steer the way.
The tour took about 5 hours in total including drive time. We spent 30 minutes or so getting acquainted with the kayaks and hearing the rules for the bay and about an hour and a half on the water. There was a small restaurant on site to get food if you get hungry and restrooms to change clothes or go the bathroom.
You will paddle 2.4 miles through a mangrove forest to get to the bio bay Laguna Grande. It was an easy paddle out because we were moving with the current. However, the paddle back required some extra work. Not only was it very windy and narrow but it was completely dark and we were going against the current. Our guides stayed with us the whole time and gave us glow wristbands on the kayaks to help light the way.
The night paddle through the mangrove was tough for new kayakers but it was our favorite part. We loved seeing the water glow in the bay, but the experience wasn’t quite what we expected. They put a large plastic tarp over us to make it as dark as possible. It worked, we did see the water glowing.
But it was a weird feeling to have a tarp over our heads and be so closely tied to our neighbor’s kayaks. Simply put, it wasn’t what we were expecting.
The part we loved the most was the night paddle back through the mangroves. The bioluminescence flowed through the waterway and we were accompanied by fireflies and fish that glowed as they were swimming. At the same time, we could hear nothing but nature sounds including coquí frogs chirping their special song.
It was truly magic!
What to bring on the Biobay kayak tour
Here’s what you should bring on your Puerto Rico bioluminescent bay kayaking tour:
- Deet-free bug spray (the bugs were so bad)
- Change of clothes
- Quick dry travel towel
- Bathing suit (it’s a good idea to wear it along with clothes you don’t mind getting wet)
- Water shoes or flip-flops
- Bag to put your wet clothes in
I wore linen pants on the trip without realizing we had to walk thigh-high into the water to reach the kayaks. I recommend wearing shorts or a cover-up that you don’t mind getting wet.
Can you swim in Puerto Rico’s bioluminescent bays?
You cannot swim in any of Puerto Rico’s bioluminescent bays at the time of this writing. Laguna Grande Bio Bay in Fajardo previously allowed you to swim but they have changed the rules to help maintain the water quality. Things like sunscreen and bug spray can contaminate the ecosystem and impact the quantity of dinoflagellates.
Hopefully, this guide to seeing bioluminescence in San Juan, Puerto Rico has helped you plan this experience! The tour is 100% worth it if you will be visiting during a new moon and enjoy outdoor activities. It was one of our favorite experiences of our week trip to San Juan and we’re so glad we got to do it.
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