The Ultimate Guide to Puerto Rico’s Bioluminescent Bays

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I’ll be real with you: the best part about traveling is, and always has been, the pictures.

Sure, there’s the electric thrill as the wheels on your plane go up signalling the start of a new adventure. There’s the euphoria of making genuine connections with other travelers in far-flung places. There’s the quiet confidence that comes from knowing that you can make your way just about anywhere, and the accomplished rush of pride the first time you string together the right words in the right order to get a cab or a cabernet in a foreign language.

All of those things are the reasons why I travel. They’re the little hits that keep me coming back for more. As travelers, we’re always chasing the next novel experience, the next crazy story, the next breath-taking view — but all of those things are exceedingly fleeting.

One of our last sunsets at Pico de Piedra in Aguada, PR.

A post shared by Kelly Chase (@kell_of_the_brawl) on


As travelers, pictures are the best tool that we have to tell our stories and catalogue our adventures. That’s why it pains me that the coolest things that I’ve seen on my travels is the one things that you can’t capture on film: swimming in a bioluminescent bay.

So what is a bio bay? Oh girl, let me just tell you:

3 Facts About Bioluminescent Bays

  1. There are only five bioluminescent bays in the world and three of them are are in Puerto Rico. The most popular, Mosquito Bay, is located on the island of Vieques off the east coast of the main island of Puerto Rico. There is also Laguna Grande on the north side of the island in Fajardo and La Parguera on the far southwestern side.
  2. The bioluminescence of a bio bay is caused by single-celled microorganisms called dinoflagellates. These microorganisms glow briefly, usually in a blue-green color, whenever they are disturbed. This means that every splash and every movement in the water causes the dinoflagellates to light up in the water around you, giving the bay its distinctive glow.
  3. There are bioluminescent dinoflagellates all throughout the ocean, however, it’s rare for them to be present in the water in concentrations high enough for them to be noticeable.

What Is It Like to Swim in a Bio Bay?

I’m about to tell you something that might blow your mind: basically every single picture that you’ve seen of a bio bay is a lie — a dirty, bold-faced lie.

If you run a quick Google image search “bio bay” you’ll be inundated with stunning images of neon blue waves lapping up on darkened beaches. Like something Lisa Frank would come out with, if she were in a goth phase. Lies. All lies.

The reality is that a bio bay is virtually impossible to photograph. This is because it isn’t the water that is lighting up, but rather the dinoflagellates in the water. These single-celled organisms light up when they’re disturbed for a brief instant and then go dark, making the overall effect impossible to capture on film.

The images that you see online are either photoshopped by the companies offering tours or they are captured using long exposure techniques, and neither end up looking anything like the real thing.

However, just because the bio bay is hard to capture on film doesn’t mean that it is at all subtle. We were lucky enough to go out on a moonless night when the bay was particularly active (our tour guide rated it an 8 out of 10 for brightness), and I have honestly never seen anything so stunningly surreal or achingly beautiful.

The waters of the bio bay don’t glow blue. On a still, quiet night, they are black with barely a hint of the magic below. As we neared the bay, the wake behind our boat began to shimmer. We laughed and plunged our hands into the water as we sped along, the spray throwing up sparks that danced in the darkness.

As we jumped into the water, all fears of the dark nighttime ocean forgotten, our splashes lit up around us, the water glowing with every movement. Once in the water if felt like the perfect ring of the night sky melted into the water. We swam through a galaxy of twinkling stars with a whole universe of stars above us.

We were a party of six adults, but we quickly became like children as we swam, laughing, through the sparkling waters. Swimming with goggles beneath the surface felt like warp speed on the Star Trek Enterprise.

We raised our arms out of the water and watched as the glowing stars dripped from our skin. It was a paradise unlike anything I’ve ever experienced, and I only hope that someday I’m lucky enough to experience it again.

Should You Swim in a Bio Bay?

Yes. Yes. Absolutely, yes. You should. I did it and it was the single most magical experience of my life. And I’ve had some magical experiences in my day.

However, there are some ethical and environmental factors to consider, and you WILL probably get some side-eye from some people when you confess to actually swimming in the bio bay.

Can you swim in a bio bay?

This is because swimming is currently prohibited in most bio bays. For example, Mosquito Bay in Vieques is such a popular destination that it can see as many as 200 visitors per night. The concern is that the chemicals on people’s bodies, like bug spray (trust me, they don’t call it Mosquito Bay for nothing) can make the waters less hospitable to the dinoflagellates. This could be detrimental to the long-term survival of the bay.

But yes, knowing all of this, I still swam in a bio bay. However, before you decide that I’m a monster, hear me out.

We booked our tour through Alelí Tours in La Parguera. We had heard mixed reports concerning whether or not swimming was allowed in the bio bay. So, we specifically asked about this when we called to book our tour, and we were told that swimming was fine.

When we arrived in La Parguera we were greeted by our guide, an attractive older gentleman (think a hunkier version of the Gordon’s fisherman) whose name was — I kid you not — Ismael. We were thrilled to discover that Ismael is a seasoned marine biologist, and we were eager to ask him all kinds of questions about the bio bay, including what is up with the whole not swimming thing.

We really, really, really wanted to swim in the water, but we weren’t trying to do anything destructive while enjoying what is definitely one of the natural wonders of the world.

Ismael dismissed those concerns immediately. He explained that he’d spent decades coming to this same bay and that there was a large amount of variation in how bright the bay was from year to year, from month to month, and even from day to day.

There are lots of factors that can contribute to this variation, but the most important one has nothing to do with environmental factors and everything to do with how bio bays are actually formed.

As our boat pulled into the bio bay at La Parguera through a narrow inlet, Ismael slowed the boat down to a crawl. He explained that while the water on either side of this inlet was 10+ feet deep, in the inlet itself it was much more shallow — usually not more than 5 feet. It was this narrow inlet that allowed the bio bay to form.

Puerto Rico Bioluminescent Bay

Turns out. that there is nothing particularly special about the water of a bio bay. Bioluminescent dinoflagellates are present throughout the ocean, however, they are just usually not in a high enough concentration to be noticeable. Bio bays then aren’t so much places where bioluminescent microorganisms live as they are where they get stuck.

Ismael explained that despite the recent alarm around the bio bays on the island being darker than usual, the reality is that this variation isn’t caused so much buy tourism as it is by much more complex ecological conditions that cause either more or fewer of the dinoflagellates to be concentrated in the bays.

If anything, a bio bay’s primary vulnerability is structural rather than chemical because of the precise conditions that need to be present for the microorganisms to get stuck there in the first place. In La Parguera, for example, the bay is surrounded by a giant ring of mangrove trees, the roots of which keep the sand bars protecting the bay in place. If those trees get ripped out in a storm (which could happen easily with one hurricane), the bio bay will be lost as well.

In the end, we decided to swim in the bio bay, and we have absolutely no regrets. We HIGHLY recommend that you give it a try, too.

Which Bio Bay in Puerto Rico is the Best to Visit?

There are three different bio bays in Puerto Rico: Mosquito Bay, Laguna Grande and La Parguera. Each has it’s own unique vibe, however, bring a healthy dose of skepticism to what you read. There are articles all over the web claiming that one is brighter than the others or better than the others, but from what I’ve experienced, these are mostly claims made by tourism boards and tour companies trying to bring more business to the area.

Our group went to La Parguera, supposedly the darkest of the bays due to over boating, but what we found was a spectacular light show and zero boats — so take what you hear with a grain of salt. At the end of the day, a bio bay is a bio bay and, provided you go there on a night when the bay is active, it’s guaranteed to be an incredible experience.

The main reason that we decided to go to La Parguera instead of the other two more popular bio bays was that as of our visit in January of 2017, La Parguera is the only bio bay that you can swim in. Being able to actually swim in the water was an experience that I would recommend to absolutely everyone and their mom, so if you get a chance, definitely check that one out.

Puerto Rico Bioluminescent Bay

The other main consideration was distance. We were on the west side of the island, so La Parguera was the closest option. As anyone who has ever spent time in Puerto Rico will tell you, although the island isn’t very big (it’s only about 100 miles wide by 35 miles long), getting around the island can be a bit of a challenge.

The main highways and high speed direct routes that we’re used to in the US are few and far between, and cabs and rental cars in Puerto Rico can be expensive. So when you’re booking your trip make sure that you factor in the time and cost of travel into your plans.

4 Things To Do When Booking a Trip to A Bioluminescent Bay

  1. Check out where the moon is in its lunar cycle. You can enjoy a biobay at any time, however, a clear night around the new moon will give you the best view of the stars above you and the bioluminescent waters below.
  2. Call ahead to see how bright the bio bay is that day, or has been lately. It’s better to call ahead and confirm that you’re going on a good night, because bio bays ebb and flow in terms of overall sparkly-ness. The subtly or intensity of the experience depends on the concentration of dinoflagellates in the water – this can fluctuate significantly due to storms, tides, season, temperature, etc. If you call ahead to some of the tour companies you can get a better sense of how the bay is looking and when will be the best time to go.
  3. Request the latest available time slot, or just ask if you can go at a time when the bay is likely to be empty (you might have to pay more). Swimming in a bio bay is magical. Swimming in a bio bay with nothing around but your boat captain and 5 of your closest friends is something approaching nirvana. We had the incredible fortune to be completely alone in the bay and it was an experience that I will treasure for the rest of my life. Later tours give you a better chance of getting to experience that for yourself.
  4. Shop around. Not all bio bay tours are created equal. Some are shorter and some are longer. Some involve booking an entire boat, while others are kayaking tours. And, probably most importantly if you’d like to really experience a bio bay, only some bio bays allow you to actually swim in the water. Some also cost more than others – our boat trip was $120 for the whole boat ($20/pp), but other tours charge $49 or more per person.

Why You Should Add Swimming in a Bio Bay to Your Bucket List

The best reason to check out a bio bay is that there is literally no other way to experience it. Pictures can’t do it justice, and no amount of description can ever give you a true sense of what it is like. You just had to have been there.

GO THERE, if you can. It’s totally bucket list worthy.

If you’d like to hear more about our Workationing adventures, be sure to check out the Workationing Podcast on iTunes or SoundCloud.

 

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20 comments

  • great article…I would like to add that the laguna grande isn’t all that great, even on a moonless night the light pollution from the near by street, hotel, etc was seen making its harder to see the light. the best was kayaking through the mangroove to reach the lagoon, it was almost pitch black and they just light up, we didn’t get to spend as much time exploring the lagoon as it was took 30min to kayak to the lagoon and then after 30min we had to go back…we took a 2 hour tour…which was too short.

    I also agree that the their website is misleading with the pictures, but this is what you would have seen with your own eyes, I plan to bring a faster lense and set it at the highest iso and see if i can get anything…or maybe put it on a long exposure.

    • Thanks for the kind words! We’ve heard that Laguna Grande wasn’t the best location, which is why we opted for La Parguera (plus, you can swim in it – a major bonus that we wouldn’t have wanted to miss).

      Our tour was also about two hours, but it only took about 15 minutes to get out there because we were in a boat with a motor. Did you mean to attach a picture? I’d love to see what you were able to capture with the lens you had – we couldn’t get any of the magic with our camera phones (and even one of our fancier cameras).

    • I had the same experience, but i spent what seemed forever on a tour bus from our cruise ship to get there, being stuck in traffic and then having it rain on us. The kayaking was fun, for me at least because 9 have SOME experience, others were flailing around with the paddles, landing in the mangroves and holding us up. The bay ws a major disappointment. The lightshow we were expecting was just a lot of hype. You wade your hand through the water and you see a little haze of bioluminescence. Not worth the time or money. Night saying through those spooky mangroves a a real thrill. They should just leave it at that

      • La Parguera is definitely where it’s at for the best bio bay experience. Not sure if it’s still there after the hurricane – it was created by mangrove trees that created a bay that trapped the plankton. If this (or a future) hurricane ripped out the mangrove trees, the La Parguera bio bay would be gone.

    • You can Google different options for La Parguera Bio Bay tours, or you can call Ishmael (our tour guide, which is included in the post). Hope you have a great time – it’s an amazing experience you won’t forget!

  • How deep is the water at the point you swam in it ? Would you say this was child friendly . I have a pretty peace four year old and a pretty timid 11 year old lol. Also do you know if certain times of the year make it brighter ? I wonder how much brighter other Bays actually are? Thanks so much for such a great article !

    • Also any restaurants or places to stay in this area you would recommend? I haven’t planned a trip in a long time and just want this to be perfect for my sons !

    • It’s scary to jump into dark water at night, even for the adults in our group! Depending on how adventurous your younger child is, your mileage may vary. But it was at least 10′ deep where we were at. From what our guide told us, this was the best bio bay on the island. There are a lot of restaurants around La Parguera – we only ate at two, so I don’t feel comfortable making a recommendation there (but Yelp will probably have you covered on that front). Enjoy Puerto Rico!

  • ***Not sure how brave got turned to peace lol but i meant brave four year old

  • Is there a particular time of the year that gives you a better chance of seeing more bioluminescence in the water? Or just go during a new moon and hope for the best?

    • Our guide told us that it mostly depends on the weather – you want it to be calm and not windy, so that the bioluminescent organisms aren’t constantly disturbed (if memory serves, each cell can only light up once every 24 hours or so). So it’d be better to go on a calm night with a brighter moon than right after a storm when there’s no moon.

  • Awesome Article and great insight. I am heading to P.R next month and been searching for the best option as to which bay to visit. Glad I came across this article. Thanks for all the hints and tips.

    • Glad to hear you found it helpful! La Parguera is where it’s at – definitely the best bio bay in Puerto Rico.

  • There are excellent bioluminescent bays in the Salt River, St. Croix, US Virgin Islands, near Falmouth in Jamaica, and at Rum Point on Grand Cayman Island. Actually the La Parguera Bay is the least bright of all of them. St. Croix is a great place to see other forms of bioluminescence including the string of pearls, light produced from crustaceans called ostracods, originally known from Panama. It makes for a fascinating night dive.

    • Thanks for the info, and comment! Night diving (even with a snorkel mask on) in a bio bay was one of the coolest things I’ve ever done.

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