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Best Night to Do the Biobay Depends on the Moon

Posted on Mar 18th, 2008 by • Updated on Feb 17th, 2014

You can skip this intro and jump straight to the calendar →

CURRENT MOON

When you visit Puerto Rico, one of the must-do things is a trip to one of our bioluminescent bays (or bio-bays). Whether you go to Laguna Grande in Fajardo in a kayak, Laguna Grande in an electric boat, Laguna Grande on a walking tour, Mosquito Bay in Vieques, or La Parguera in Lajas, you’re sure to have an experience that you will never forget.

In case you want to try to capture some memories of the biobay in pictures, we’ve written a primer for taking photos in the biobay. Note that you’ll need a camera with lots of manual settings — you’ll need to be able to control the length of exposure, the aperture setting (f-stop), and the ISO/ASA film speed setting.

The health of the biobays is measured by the number of dinoflagellates per unit of water. That measure translates into how "bright" the bay will be. Mosquito Bay is the most healthy. La Parguera is the least healthy. The Department of Natural Resources has taken steps to maintain and improve the health of Laguna Grande.

In any case, the biobay is best experienced on a cloudy or moonless night. While we can’t predict if there will be clouds, we can do a pretty good job of predicting the phase of the moon and the time the moon rises. Those are the main two factors that come into play. In general, it’s best to avoid the 5 to 8 nights prior to the full moon.

The better bio-bay tour operators will be able to tell you in advance if the night you’ve chosen will be a good night, with regard to the phase of the moon and moonrise. Many operators will not even conduct tours on less-than-optimal nights. Others will bring a tarp to use to block out the moonlight.

To help you with your planning, we’re providing the calendar below which indicates the new and full moons, and our opinion of which nights will be better or than others.

   New Moon     Best     Good     Fair     Bad     Full Moon
   Fair Early, Bad Later     Best Early, Good Later     Good Early, Fair Later 
NOV 2014
SMTWTFS
1
2 3  4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30
DEC 2014
SMTWTFS
1 2 3  4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30 31
JAN 2015
SMTWTFS
1 2 3
 4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
FEB 2015
SMTWTFS
1 2 3  4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
MAR 2015
SMTWTFS
1 2 3  4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
APR 2015
SMTWTFS
1 2 3  4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30
MAY 2015
SMTWTFS
1 2
3  4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19 20 21 22 23
24 25 26 27 28 29 30
31
JUN 2015
SMTWTFS
1 2 3  4 5 6
7 8 9 10 11 12 13
14 15 16 17 18 19 20
21 22 23 24 25 26 27
28 29 30
JUL 2015
SMTWTFS
1 2 3  4
5 6 7 8 9 10 11
12 13 14 15 16 17 18
19 20 21 22 23 24 25
26 27 28 29 30 31
AUG 2015
SMTWTFS
1
2 3  4 5 6 7 8
9 10 11 12 13 14 15
16 17 18 19 20 21 22
23 24 25 26 27 28 29
30 31
SEP 2015
SMTWTFS
1 2 3  4 5
6 7 8 9 10 11 12
13 14 15 16 17 18 19
20 21 22 23 24 25 26
27 28 29 30
OCT 2015
SMTWTFS
1 2 3
 4 5 6 7 8 9 10
11 12 13 14 15 16 17
18 19 20 21 22 23 24
25 26 27 28 29 30 31
   New Moon     Best     Good     Fair     Bad     Full Moon
   Fair Early, Bad Later     Best Early, Good Later     Good Early, Fair Later 
Updated 28-Nov-2014 07:28am AST.

 

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78 comments
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  1. We’re considering going on Dec 21 when the moon is full, but there is supposed to be a total lunar eclipse. Will this be a good day because of the eclipse or not?

  2. Dec 21, 2010 is the night of the full moon. In general, this would be a bad night. Depending on the time and duration of the lunar eclipse, it may or may not be a good night to go to the biobay.

  3. while I have heard that also, the night I went was a cloudless full moon night and our excursion leader @ fajardo said he had never seen the biobay so bright, and it was stunning!

  4. http://www.puertoricodaytrips.com/biobay-and-moon/#mooncalendar
    Why does this lunar calendar look so different from this lundar calendar
    http://www.moonconnection.com/moon_phases_calendar.phtml
    Is July 26 2013 a good night to do bioluminescent kayak tours or not?

  5. The difference is ours is a baybay viewing calendar and the other is a moon phase calendar. We take into account the time of the moon rise and how much light there is and how it will affect viewing.
    The 26th will be great night for the biobay. Yes there is a large moon, but it only rises at 10pm. So it won’t be very bright during biobay trip times, especially not for the first trip out.

  6. we are planning to stay a few nights in PR before our cruise departs from the island: oct 18-20, 2013. this is a full moon, and the aftermath of a full moon. would you advise to go friday (18th), saturday (19th), or will it really not be optimal viewing this time? we have waited two years to do this, and are disappointed it’s during a full moon. thank you!

  7. Well, it is a full moon, but if you really want to do it, I would go on the first tour of the night on Saturday the 19th. The full moon rises at 6:30pm, so it will not be overhead then and maybe the trees will block some of the light. You can always hope for clouds!

  8. thank you very much for your detailed info! it will definitely help us plan our trip. with the government shutdown, it now seems we will have more time since many things could be closed. all of this will be good to know. many thanks again!

  9. We’re planning to the go to the trip on Dec 20. It shows “Best Early, Good Later”. So when is the best time for it? As early as like 6:30?

  10. Yes, go on the first tour of the evening, which is usually around 6:30pm.

  11. Is Feb 7th 2014 still shaping up to be a Fair evening – our trip seems to be happening right during the poor viewing time. I didn’t know how often you updated the calendars or if it is fixed. Thanks!

  12. Yes, unfortunately, it will only be fair. The moon rises early in the day, so it will be directly overhead at 7:15pm. But I think they try to go toward the edges, where branches may block some moonlight. And you can always hope for a cloudy night!

  13. Hi we are going to Vieques from the 14-17 Feb which all seem to be full moon nights. Will you guys be having bio bay tours in any of those nights?

    Also is the tour only offered by kayak or a small group boat – I dont know how to swim so am a bit scared of kayaking myself in the dark.

  14. Sana- you will have to contact the tour company to check if they go during full moons. We don’t run the tours, we just report on our experience and give our opinions. Depending on the bio bay you want to visit, there are tours via kayak, electric boat (small ones in Fajardo, a larger one for Vieques), and there is even a walking tour at La Cabezas to see the bay on foot. In Parguera they still use motor boats and have them in small and large sizes.

  15. Our trip is Feb 9-15 which is a bad time for the moon. As this seems like an incredible experience I’d like to go one night and hope for clouds! Would you recommend a certain night or time of night to go during this week? Maybe the early tour the first night Feb 9th? Or 10th? I found a tour company that uses a tent, is that effective?

  16. Yes, bad timing. Go on the 9th, it would be your best hope and/or try the company with the tarp…it has to help!

  17. We are in the planning stages of a week long trip to Vieques in May. Our anniversary falls on the 7th, which only gives us the 5th and 6th as possible days. I would consider foregoing the actual date of our anniversary in order to get to experience the best bay viewing, but if we come later in the month, won’t we be increasing our chances of rainy season ruining our trip?

  18. I was planning on going March 17, 2014… Is this a bad day to go?

  19. There will be lots of moonlight. Some companies don’t go at all, some go but use tarps to block the light.

  20. We plan a trip for March 27 2015. Can you give me any idea if the bio luminous kayak experience will be poor because of the half moon phase?

  21. We believe it will be a fair night (not good or great) because of the time the moon rises. The moon will be about 60% bright and directly overhead at 7pm. :-(

  22. May has always been one of PR’s rainiest months. But you never know. Vieques gets less rain than other places in PR, so there is no telling if rain will be a problem. Pick you travel dates and hope for the best.

  23. We will be staying near Fagardo on April 7th, 8th and 9th – all bad nights as per the calendar. Would hate to not try it so when and where would you suggest?
    Thanks

  24. I would try the 7th in Fajardo (currently the Vieques BioBay is not sparkling well). Ask if the company uses a tarp or something to block the moon light.

  25. We’re here now. The only days available for us to take the bio bay trip are the 10th and 11th. Any advise for our best opportunity to see the bay?

    Thanks,
    Mike

  26. Ouch. Well, the moon will be directly overhead at 9:16pm on the 10th. It will be 82% bright.
    The 11th, it will be overhead at about 10pm, but 90% bright.

    I guess I would say go to the 1st trip on the 10th or the 11th. You could ask if the operator uses a tarp to block some of the moonlight.

  27. We want to do a Bio Bay tour on April 19, 2014. Will this be a good night and what company do you recommend?

    Thank you

  28. According to the calendar, yes, the 19th is a great night to see the biobay. We have used Kayaking Puerto Rico and liked them very much.

  29. we will arrive San Juan on 4/11 night and leave 4/19 early morning and we come to see the biobay. could you give us a recommendation on the night , the bay and the company that we should go for? we will plan the rest of our trip around this. Thank you!

  30. The 17 or the 18th would be the best. Who you go with depends on how you want to experience it and which bay you want to go see.
    There is the bay in Fajardo, which can be done on a kayak, electric boat or walking, or Vieques Biobay, which has to be done with East Island Excursion (unless you want to stay on Vieques overnight). This article should help you: http://www.puertoricodaytrips.com/fajardo-bio-bay/

  31. thanks a lot. I will go on 18th. I would like to know which bio bay is brighter right now. Mosquito Bay in Vieques or Laguna Grande in Fajardo? or they are about the same after what happened to Mosquito bay.

  32. I have heard they are about the same right now, but Mosquito Bay should continue to improve, making it brighter every day.

  33. Our trip is May 10 – 14 which is a bad time for the moon. As this seems like an incredible experience I’d like to go one night and hope for clouds! Would you recommend a certain night or time of night to go during those 5 days? Do you recommend early tour or late tour? Thanks in advance

  34. While they are all not good, if you go on the earliest tour on the 10th, the moon will be least bright. Or the earliest tour on the 13th, the moon will be lower in the sky (though brighter).

  35. We are planning to go to the Biobay in Vieques Island on May 11 and stay there that night. I was told that they are currently experiencing some problems with the bay and it is about 60-75%. Is it still worth going? We want to take the Kayak tour. Thanks

  36. Even at 60%, the Vieques biobay is the brightest around. Well worth going. However, if you mean May 11 of 2014, the moon will be really bad for viewing. I am not sure anyone goes out on bad nights, but you can call and ask. I am not sure going to any biobay when the moon is that bright and overhead is worth it.

  37. We are planning to visit Puerto Rico from May 12th to May 17th and planning to go to Fajardo bio bay on May 15th, did not want to go on May 16th since it was close to the end of our trip.
    Do you think it is worth going to the bay on the 15th at 6pm or should we go later in the evening?

  38. Well…the almost fill moon will rise at about 8pm, so the first tour would be the best that night. The sky may still be very bright before it comes up, but it will probably be ok.

  39. Thanks Gwenn, would you think it makes more sense to go on Friday?

  40. The first tour Friday would be better viewing since the moon comes up later, after the tour.

  41. Thank you for posting this! I was hoping you could help us too: we are going June 8-14 (worst time for Bio Bay!) but for June 13th, this link says that moonrise is at 9:37: http://www.timeanddate.com/worldclock/astronomy.html?n=234&month=6&year=2014&obj=moon&afl=-11&day=1. If we go on the earlier tour, will we be able to see the bay light up, since the moon rises later?

  42. You need to change the location to San Juan for the moonrise chart. So on June 13th, the full moon will rise 7:39pm. The fist tour would be pretty good that night since the moon will be lower in the sky.

  43. Hi Gwenn, thanks for posting this. We are planning to go to Vieques on July 5th or 6th. Is that a bad time?

  44. It is not the best for viewing- call ahead to make sure they are going out those nights (some don’t go if the moon isn’t right). The 5th is better than the 6th.

  45. Hi, I want to book a tour for the 6/7 or 6/9 this coming week. The calendar says that those days are bad for viewing, but out of those two dates which one is the better day to do it?

  46. Go on the first (early- around 6:30-7pm)) trip on the 7th.

  47. Hi, I wanted to book for June18th or 19th on the electric boat since I am not an experienced kayaker. What time would be best and how far are you from the airport?

  48. I hope you were able to call them directly and get a reservations. They sell out quickly.

  49. We are coming to Puerto Rico on July 7 – July 12. I have looked at the moon calendar and it is showing bad for viewing. I’m so disappointed, any suggestions? Thanks!

  50. We kayaked Fajardo in 2008 and loved it so much we want to take my motherinlaw. We will be cruising so our dates are limited to Saturday. 7/12 or Sunday 7/20. Wanted to walk into Laguna grande but it appears they are closed Sunday. Mom is 78 so we considered electric boat, but they are not offering July tours on website. Emailed captain Suarez but no response. Any suggestions? We really want to do it Sunday so we can show mom osj Sunday morning and stick to osj befor cruise departs. Any suggestions? Thanks in advance!

  51. For the electric boats, it is best to call them. Emails are not their thing. I believe Suarez goes out on Sunday nights. But try calling a few times if you can’t get through to a person (messages are not always answered)….they are sometimes hard to get in touch with!

  52. Try to get the first trip on the 7th, or maybe the 8th. After that the moon is brighter each night. And pray for a cloudy night!

  53. Hi we are planning to visit PR to see the bio bay on either the second week 10-15 or third week 17-21 of November 2014. The second week is just after the full moon . Would the third week be better? Will there be a lot of rain in November? Thanks!

  54. Either week is great for viewing the bays. Rain-from my experience, we usually we get more rain starting later in Novemeber. But you can never tell with the weather! November still has a possibility of hurricanes, but it is not too likely. Choose whichever week works best for your schedule. We have a holiday in either week (Veteran’s Day and then Discovery Day).

  55. we are going to pr and staying in san juan. want to see the biolum bay but of course…full moon.
    we are there august 8,9,10 as our full days. which would be best or is it not even worth going to see ..(would prefer to go 9th or 10th as our first full day is 8th)?
    thanks

  56. Out of those days, the 8th is the best, and go the 1st tour possible. Moon rises at 5pm, but it is bright. But it will be closer to the horizon during the first tour.

  57. Hi! We will be in Vieques 28th of December to the 3rd of January. Other then wishing for a cloudy night (no rain of course) what would be our best bet for the bio bay?
    Gracias!

  58. The 28th or 29th are the least bright days while you are there (28th being the better night).

  59. Hi
    I will be in PR from oct 4-6,2014.
    Which night should is my best option?
    Should I take the early or late trip?
    Thanks in advance!

  60. Hi
    I will be in PR from oct 4-6,2014.
    Which night should is my best option?
    Should I take the early or late trip?
    Thanks in advance!

  61. Wow- none are going to be great. If you can get it- the first tour on the 4th would be the best. If that is not available, the first tour of those nights would be better than the later tour. Also check that the company you will use does something to block the light- maybe a tarp or something.

  62. We are planning a trip to Fajardo, PR from Dec. 30, 2014-Jan. 6, 2015. Unfortunately, the moon will be full most of those nights. In your opinion, which date and time would be best to take a bio-bay tour?

  63. Well, they all are not great. The first tours on the 30th or 31st or the 1st. Ask if they use tarps or something to help block the sunlight.

  64. Best option (though they all are not good) would be 1st trip on the 4th. First trip on the 5th would be second choice.

  65. Hi,

    We are visiting Nov15-22 2014. Looks like these are all great nights to see the biobay. I am wondering if there is still ant difference between these nights. Is it the later the better? We may be able to visit Vieques during our first couple nights but not sure if we should wait till later in the week.

  66. All great nights means no real difference in viewing since the moon is out during that time. Go when it is convenient for you. I would try to go to the Vieques biobay while you are there.

  67. Hi,
    We are visiting pr next week september 19th. Can you tell me what times do the tours start for bio bay?

  68. You have to visit the biobay after dark. This time of year (September), it gets dark around 6:30pm … so I imagine the first biobay tours would start out around 6pm.

  69. Hi Gwenn and Ray,

    How are the biobays recovering this year? We are going between Nov 15-22nd. All are great nights. But we are trying to decide between taking a electric boat to Mosquito biobay or kayak at Fajardo biobay. Is the Mosquito bay much brighter than Fajardo bay this year?

    Thanks!

  70. The bays are back to normal. All recovered! So as long as there are no setbacks, Vieques bay is brighter than Fajardo.

  71. Our family will have a cruise vacation and will stay in San Juan at Nov. 28, 29 and Dec 7. Unfortunately, they are not perfect days for bio bay tour but that’s the best we could do. Our flight will arrive SJU at 3PM. The ferry to Vieques is on 4:30PM and 8:00PM. Is it possible for us to catch the Vieques bio bay tour on Nov 28 (the only good day)? If not, do you suggest the tour in Fajardo on Nov 28 (good day) or the tour in Vieques on Nov 29 (fair day)? The moon calendar on http://www.biobay.com/ says Dec 7 is a good day, which will be perfect for our travel plan if it is true. Do you have any suggestion on it? Thanks a lot for the help.

  72. Well, if it were me, I would do Fajardo biobay on the 28th. It is not possible to do the Vieques biobay on your own on the 28th- too rushed for time. You could check with East Island Excursions if they could get you there that night (but I think no).
    The 7th seems too bright to me- The moon rises at 7pm and it is 99% full brightness.

  73. Hi Gwenn,

    Thanks a lot for the suggestions and we will go Fajardo biobay on Nov 28th. Is it better to have a late night tour or early night tour on that day?

  74. Early tour if you can do it, but later will be ok too.

  75. I will be visiting PR 12/7-12/10. I wanted to visit one of the Biobays… I was planning on going the 9th as it seems it will be a good day to go. Which bay do you feel is the best to visit? Also, I am staying in San Juan so if you could share the distance to the bay you suggest, it would be helpful.

    Thanks,

    Nicole

  76. Most people go to the Fajardo biobay- it is closer/easier and cheaper than getting to the Vieques biobay. The drive to Fajardo will take about 1-1.5 hrs, depending on traffic. You can drive yourselves, or many of the tour companies can provide transportation.
    If you want to go to the Vieques biobay, you need to go with East Island excursions. They are the only ones that can do it in one evening.

  77. The only time I could get off to travel was the 5th to the 8th of December. I was looking forward to the bio bay trip and now that I stumpled upon this site and the moon calendar I’m kind of bummed. Any suggestions?

  78. The first trip out on the 7th would be your best bet. Ask the if company uses tarps or something to help block some moonlight.

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