Bio Bay nights ✨
A dredged cove off the North Sound near Rum Point where the water glows blue when you stir it, thanks to a dinoflagellate called Pyrodinium bahamense. It is one of about a dozen such bays in the world, and the only rule that really matters is darkness: the glow is best when the moon is down.
Best nights in the next two weeks: Friday 6 Nov (dark and glowing), Saturday 7 Nov (dark and glowing), Sunday 8 Nov (dark and glowing).
Tonight5 Nov🌘Excellentrises 04:04Tomorrow6 Nov🌘Excellentrises 04:57Sat7 Nov🌑Excellentrises 05:51Sun8 Nov🌑Excellent0% litMon9 Nov🌑Excellent1% litTue10 Nov🌑Excellent3% litWed11 Nov🌒Excellentsets 19:33Thu12 Nov🌒Goodsets 20:24Fri13 Nov🌒Goodsets 21:18Sat14 Nov🌒Goodsets 22:11Sun15 Nov🌓No tourssets 23:03Mon16 Nov🌓No tourssets 23:55Tue17 Nov🌓No tourssets 00:46Wed18 Nov🌓No tourssets 01:37
Night by night
| Night | Moon | Lit | Moonrise / set | Dark from | Rain | Wind | Verdict | Why |
|---|---|---|---|---|---|---|---|---|
| Tonight 5 Nov · kayak window | Waning crescent | 10 % | ↑ 04:04 | 18:38 | 90 % | 11 kt | Excellent | Moon below the horizon all evening. Showers likely (90%); light rain is fine, tours run. |
| Tomorrow 6 Nov · kayak window | Waning crescent | 5 % | ↑ 04:57 | 18:37 | 49 % | 12 kt | Excellent | Moon below the horizon all evening. |
| Sat 7 Nov · kayak window | New moon | 2 % | ↑ 05:51 | 18:37 | 22 % | 12 kt | Excellent | Moon below the horizon all evening. |
| Sun 8 Nov · kayak window | New moon | 0 % | down all evening | 18:37 | 43 % | 10 kt | Excellent | Moon below the horizon all evening. |
| Mon 9 Nov · kayak window | New moon | 1 % | down all evening | 18:37 | 47 % | 10 kt | Excellent | Moon below the horizon all evening. |
| Tue 10 Nov · kayak window | New moon | 3 % | ↓ 18:43 | 18:36 | 44 % | 13 kt | Excellent | Moon below the horizon all evening. |
| Wed 11 Nov · kayak window | Waxing crescent | 7 % | ↓ 19:33 | 18:36 | 65 % | 9 kt | Excellent | 7% moon sets 19:33: darker after that, take the later tour. Showers likely (65%); light rain is fine, tours run. |
| Thu 12 Nov · kayak window | Waxing crescent | 13 % | ↓ 20:24 | 18:36 | 71 % | 4 kt | Good | 13% moon sets 20:24: darker after that, take the later tour. Showers likely (71%); light rain is fine, tours run. |
| Fri 13 Nov · kayak window | Waxing crescent | 20 % | ↓ 21:18 | 18:36 | 55 % | 5 kt | Good | 20% moon sets 21:18: darker after that, take the later tour. |
| Sat 14 Nov | Waxing crescent | 28 % | ↓ 22:11 | 18:36 | 38 % | 12 kt | Good | 28% moon sets 22:11: darker after that, take the later tour. |
| Sun 15 Nov | First quarter | 37 % | ↓ 23:03 | 18:35 | 53 % | 14 kt | No tours | 37% moon up all evening. Too bright: operators usually skip nights like this. |
| Mon 16 Nov | First quarter | 46 % | ↓ 23:55 | 18:35 | 62 % | 11 kt | No tours | 46% moon up all evening. Too bright: operators usually skip nights like this. Showers likely (62%); light rain is fine, tours run. |
| Tue 17 Nov | First quarter | 56 % | ↓ 00:46 | 18:35 | 53 % | 12 kt | No tours | 56% moon up all evening. Too bright: operators usually skip nights like this. |
| Wed 18 Nov | First quarter | 66 % | ↓ 01:37 | 18:35 | 43 % | 14 kt | No tours | 66% moon up all evening. Too bright: operators usually skip nights like this. |
Moon times are computed for the bay itself (19.373, -81.271, approximate). The tour window used is 19:00 to 22:30. Weather is the daily outlook for Grand Cayman; rain and wind are the day's values, not the evening's.
How to read it
- Moon first. Nights with the moon below the horizon for the whole tour window score 100. Moonlight up in the window costs points in proportion to how bright it is and how long it is up. When the moon is up for more than half the window and more than 30% lit, operators generally do not run, and we say so.
- Time your tour to the moon. A waning moon rises late, so the early tour is dark. A waxing crescent sets early, so the later tour is darker. The table gives the rise and set times.
- Rain. Light rain is fine and tours run; the kayak operator cancels only at check-in for safety. A heavy downpour the day before adds fresh water and can dim the glow for a night or two.
- Wind is about the paddle back, not the glow. The bay is sheltered; the return against an evening north-easterly is the hard part.
- Cloud on a moonlit night hides some of the moon. We give it a small credit, nothing more.
Going
- Cayman Kayaks from Rum Point (Sand Point Road): double and clear kayaks and an electric boat, about 90 minutes, check-ins around 19:20 and 21:20, run only on the dark nights of each month. Their published windows: 2026-09-30 to 2026-10-15, 2026-10-28 to 2026-11-13, 2026-11-26 to 2026-12-13 (from their tours page, 2026-11-01).
- Boat tours leave from Kaibo (White Sand Water Sports, with Starfish Point on the way), the Cayman Islands Yacht Club (George’s Watersports, about 20 minutes across the Sound), Camana Bay and Safehaven.
- No DEET, reef-safe lotion only, and most operators ask you not to swim: jellyfish, and the water gets stirred up. Stirring with a paddle or your hand is the show.
- The bay is the only bioluminescence tour site in the islands; there is no equivalent on the Brac or Little Cayman.
Moon rules are inferred from the kayak operator’s run windows; weather rules are our starting guesses and will be tuned with operators. Nothing here is a booking or an official forecast.