Vieques bio bay (Mosquito Bay)

Book a dark night near the new moon: tours on Vieques cost $70, or $195 as a same-day trip from Fajardo. Guinness cites up to 700,000 dinoflagellates per gallon in Mosquito Bay.

Updated October 22, 20265 operators compared19 sources

Mosquito Bay on Vieques at night, ringed by mangroves
Photo: Edgar Torres, CC BY 3.0

Quick picks

Bio bay nights, next 30 days

The glow is easiest to see when the moon is down during tour hours, roughly 7:30 to 10 pm. The next run of dark evenings is Oct 30 to Nov 12. Estimated from the moon's phase and typical rise times, so treat it as a guide and check the forecast for clouds.

  1. Fri Oct 23Bright, 95% of the moon lit
  2. Sat Oct 24Bright, 99% of the moon lit
  3. Sun Oct 25Bright, 100% of the moon lit
  4. Mon Oct 26Bright, 99% of the moon lit
  5. Tue Oct 27Bright, 96% of the moon lit
  6. Wed Oct 28Bright, 91% of the moon lit
  7. Thu Oct 29Some moon, 84% of the moon lit
  8. Fri Oct 30Dark, 76% of the moon lit
  9. Sat Oct 31Dark, 66% of the moon lit
  10. Sun Nov 1Dark, 56% of the moon lit
  11. Mon Nov 2Dark, 45% of the moon lit
  12. Tue Nov 3Dark, 35% of the moon lit
  13. Wed Nov 4Dark, 25% of the moon lit
  14. Thu Nov 5Dark, 16% of the moon lit
  15. Fri Nov 6Dark, 9% of the moon lit
  16. Sat Nov 7Dark, 4% of the moon lit
  17. Sun Nov 8Dark, 1% of the moon lit
  18. Mon Nov 9Dark, 0% of the moon lit
  19. Tue Nov 10Dark, 1% of the moon lit
  20. Wed Nov 11Dark, 5% of the moon lit
  21. Thu Nov 12Dark, 10% of the moon lit
  22. Fri Nov 13Some moon, 18% of the moon lit
  23. Sat Nov 14Some moon, 27% of the moon lit
  24. Sun Nov 15Some moon, 36% of the moon lit
  25. Mon Nov 16Bright, 47% of the moon lit
  26. Tue Nov 17Bright, 57% of the moon lit
  27. Wed Nov 18Bright, 68% of the moon lit
  28. Thu Nov 19Bright, 77% of the moon lit
  29. Fri Nov 20Bright, 85% of the moon lit
  30. Sat Nov 21Bright, 92% of the moon lit

Dark: moon down or nearly new Some moonlight Bright moon

Every option side by side

Operator What you get From Length Group Min ageCancellation Book
Abe's Snorkeling & Bio-Bay Tours
Biobay Tour
$70 per adult
2 hours
All ages welcome
No refund within 24 hours; groups of 10+ must cancel a week out; weather cancellations get reschedule or full refund.
 Check dates
Black Beard Sports
Vieques Bio Bay Clear Kayak TourIncludes Tandem clear-bottom kayak, Paddles and life vest, Guide, Drinking water, Round-trip transportation
$70 per person
About 2.5 hours total, about 1 hour kayaking
Maximum 10 guests
5+
1-5 people: full refund 24+ hours out; 6+: one week. Light rain does not cancel; unsafe weather does.
 Check dates
Kayaking Puerto Rico
Vieques Bio Bay Same Day Boat AdventureIncludes Round-trip boat Fajardo to Vieques, Ground transport to Mosquito Bay, Guided tandem glass-bottom kayak, Life jackets, Light snacks and soft drinks on the boat, About 1 hour free time in Esperanza
$195 per person
About 7 hours including check-in
10+
Refers to Kayaking Puerto Rico FAQ: full refund 48+ hours out; operator decides weather cancellations.
 Check dates
JAK Water Sports
Bioluminescent Bay Tour (clear-bottom kayak)Includes Interpretive guide, Kayak briefing and paddling instruction, Tandem clear-bottom kayak, Star constellation interpretation
Not listed
Approx. 2 hours 15 minutes including check-in
4+ (no children under 4 on kayak tours)
Groups of 4 or fewer: free cancel by 10 AM tour day; 5+: 48 hours. Not cancelled for rain.
 Check dates
Taino Aqua Adventures
Bioluminescence tour (transparent kayak)
Not listed
Check dates

From each operator's own website, checked October 22, 2026. How we compare.

Calle Flamboyán in Esperanza and the Ceiba ferry

Esperanza's Calle Flamboyán is the check-in street for most Mosquito Bay tours. JAK Water Sports meets at number 136, across from the Malecón and next door to the Vieques Conservation and Historical Trust, and sends drivers to dirt lots by the fishing pier and El Blok Hotel. Abe's meets across from Rainbow Realty at 278 Calle Flamboyán. Black Beard Sports picks guests up across from El Blok or at its store in Isabel II, near the ferry landing, and drives them to the bay.

Puerto Rico Ferry sails to Vieques from its Ceiba terminal at Marina Dr. Roosevelt Roads and puts the crossing at about an hour. Its official itinerary for August 1 to November 30, 2026 lists eight sailings from Ceiba on weekdays and six on weekends, the last at 8 pm. The final boat back leaves Vieques at 9:30 pm every day. Discover Puerto Rico also lists a flight of about 25 minutes from Isla Grande airport in San Juan.

Kayaking Puerto Rico's same-day trip from Fajardo avoids the ferry. Its boat leaves Marina Puerto Chico, with check-in at 4:30 pm and departure at 5 pm from September to November, and the outing lasts about 7 hours with roughly an hour free in Esperanza. Ferry travelers face a tighter clock. JAK says a same-day ferry return may work only with its earliest tour, and Abe's says summer guests must stay overnight on Vieques.

Pyrodinium bahamense in a narrow-mouthed mangrove bay

Guinness World Records named Mosquito Bay the brightest bioluminescent bay in 2006, citing up to 700,000 dinoflagellates per gallon (4.5 liters) of water. They belong to Pyrodinium bahamense, which a 2024 study in Revista de Biología Tropical calls the dominant species in Puerto Rico's bio bays. Disturbed, they flash blue-green, and each flash lasts about a tenth of a second. Guinness credits the narrow mouth with keeping them in the bay and decaying mangroves with feeding them. A monthly survey in 2003, published in 2006, averaged 286,411 Pyrodinium cells per liter here over the year.

Hurricane Maria left the bay dark for weeks, NPR reported in December 2017. The storm poured fresh water into the salty bay and upset its chemistry, and its winds may have swept water and dinoflagellates out of the cove. By the time of the report the glow had come back, though far dimmer than normal, and NPR noted that recovery after earlier hurricanes had taken months. The Vieques Conservation and Historical Trust takes weekly samples to track the bay.

The water glows most vividly on dark nights around the new moon, Black Beard Sports says, and brightness shifts from night to night with the weather. JAK Water Sports runs no tours the day before, the day of or the day after a full moon. Its guides also explain the constellations and point out fish lighting their own way. In January 2014 scientists blamed a dip in the bay's glow on strong seasonal swells and tidal surges, El Nuevo Día reported.

Swimming ban and DEET-free repellent at Mosquito Bay

Swimming is not permitted in Mosquito Bay, according to Discover Puerto Rico, which says the bay is reached by kayak only. The bay is a DRNA-protected area co-managed by the Vieques Conservation and Historical Trust, Primera Hora reported in 2022. Jet skis and motorboat tours are barred inside it, and licensed concessionaires run the tours, mostly in kayaks. In 2014 the DRNA ordered its rangers to step up patrols against unauthorized kayak operators taking visitors into the bay.

Rain alone does not stop tours at JAK Water Sports or Black Beard Sports. JAK makes its own weather calls, and Black Beard cancels only for unsafe conditions such as high winds or thunderstorms. Black Beard says mosquitoes stay on shore rather than out on the water. JAK calls repellent optional, asks for DEET-free products to protect the dinoflagellates, and sells them at its shop.

Abe's takes all ages, JAK Water Sports no children under 4, and Black Beard Sports children from 5 who can sit in a tandem with an adult. JAK caps each kayak at 385 lbs with no one over 280 lbs; Black Beard allows 400 lbs per kayak. Kayaking Puerto Rico's same-day trip takes ages 10 and up, has a 230 lb limit, and excludes pregnant guests. JAK suggests a long-sleeved shirt and shorts that can get wet, with flip-flops or Crocs that come off on shore and ride in the kayak.

Clear kayaks in Esperanza or Fajardo's $195 boat

Abe's and Black Beard Sports both list $70 (Black Beard adds tax). Abe's charges $50 for ages 4 to 11, lets infants go free, and runs 2-hour tours at 6, 7, 8 and 9 pm. Its page does not name the kayak type. Black Beard uses clear-bottom tandems, caps groups at 10 and includes the van to the bay, for about 2.5 hours in all with roughly one hour paddling. Parties of up to 5 get a full refund with more than 24 hours' notice.

JAK Water Sports and Taino Aqua Adventures also paddle clear kayaks, but neither showed a price on the pages checked. JAK's tour lasts about 2 hours 15 minutes including check-in. Groups of 4 or fewer can cancel free until 10 am on the tour day, larger groups need 48 hours, and same-day bookings are non-refundable. Taino's home page gives an Esperanza address on Flamboyán but no tour details.

Kayaking Puerto Rico's same-day trip costs $195 plus taxes and fees and runs about 7 hours from Marina Puerto Chico in Fajardo. The price covers the boat both ways, ground transport to the bay, a guided glass-bottom tandem kayak, and light snacks and soft drinks aboard. Bookings run through a FareHarbor account named funcatpr, and the tour page does not say who operates the boat.

Before you book

  • Buy ferry tickets ahead online or in the City Experiences app. Puerto Rico Ferry sells advance tickets to non-residents only there, releases any remaining seats at the terminal window on the day, and treats all sales as final.
  • Pack light for the ferry: one small carry-on rides free, but a beach cooler or a bicycle costs $2 per trip.
  • Check the moon before booking. JAK Water Sports runs no tours the day before, the day of or the day after a full moon.
  • Leave the phone behind. Black Beard Sports says the glow is hard to photograph and keeps anything not needed on the water in the van with the driver.
  • Getting there. Discover Puerto Rico lists two ways from San Juan: a flight of about 25 minutes from Isla Grande airport, or a ferry from Ceiba. On the island, it says, most bio bay tours leave by bus from the center of Esperanza.

The operators

Black Beard Sports

from $70 per person

Vieques Bio Bay Clear Kayak Tour

Length
About 2.5 hours total, about 1 hour kayaking
Group
Maximum 10 guests
Age
5+
Weight
400 lbs combined per kayak

Clear-bottom kayaks only

Check datesAll details

Kayaking Puerto Rico

from $195 per person

Vieques Bio Bay Same Day Boat Adventure

Length
About 7 hours including check-in
Age
10+
Weight
230 lbs per participant

Same-night round trip from Fajardo, no ferry or overnight stay needed

Check datesAll details

JAK Water Sports

Price on request

Bioluminescent Bay Tour (clear-bottom kayak)

Length
Approx. 2 hours 15 minutes including check-in
Age
4+ (no children under 4 on kayak tours)
Weight
385 lbs combined per kayak, no single person over 280 lbs

No tours the day before, day of, or day after a full moon

Check datesAll details

Head to head

Sources

Prices and policies come from each operator's own pages, read on October 22, 2026. Seasons, rules and local details come from the pages below.

  1. jakwatersports.com/biobay-tour
  2. abessnorkeling.com/tours/biobay-tours/biobay-tour
  3. blackbeardsports.com/vieques-bio-bay-kayak-tour
  4. puertoricoferry.com/routes-schedules/ceiba-vieques
  5. puertoricoferry.com/wp-content/uploads/2026/06/...
  6. discoverpuertorico.com/es/articulo/...
  7. kayakingpuertorico.com/bio-bay-vieques-tour
  8. guinnessworldrecords.com/world-records/...
  9. archivo.revistas.ucr.ac.cr/index.php/rbt/article/view/56729
  10. npr.org/transcripts/573000699
  11. cienciapr.org/es/printpdf/11989
  12. scholar.uprm.edu/entities/publication/...
  13. discoverpuertorico.com/...
  14. primerahora.com/estilos-de-vida/ph-mas-familia/...
  15. discoverpuertorico.com/article/...
  16. tainoaquaadventures.com
  17. puertoricoferry.com/faq
  18. puertoricoferry.com/rates
  19. vieques.com/vieques-ferry