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Grand Cayman Bio Bay in August 2027: darkest nights

Boat tours leave from Rum Point and Kaibo. Operators cancel on bright full-moon nights. Year-round.

15 pitch-dark nights, 17 dark nights

New moon Mon 2 Aug, Tue 31 Aug · Full moon Tue 17 Aug

Night by night, August 2027

NightMoon19:0020:30Best
Sun 1 Aug 0%●●●●●●●●●●20:30
Mon 2 Aug 1%●●●●●●●●●●20:30
Tue 3 Aug 4%●●●●●●●●●●20:30
Wed 4 Aug 11%●●●●●●●●●●20:30
Thu 5 Aug 19%●●●●●●●●●●20:30
Fri 6 Aug 28%●●●●●●●●●●20:30
Sat 7 Aug 38%●●●●●●●●●●20:30
Sun 8 Aug 49%●●●●●●●●●●20:30
Mon 9 Aug 59%●●●●●●●●●●20:30
Tue 10 Aug 69%●●●●●●●●●●20:30
Wed 11 Aug 78%●●●●●●●●●●20:30
Thu 12 Aug 85%●●●●●●●●●●20:30
Fri 13 Aug 91%●●●●●●●●●●20:30
Sat 14 Aug 96%●●●●●●●●●●20:30
Sun 15 Aug 99%●●●●●●●●●●19:00
Mon 16 Aug 100%●●●●●●●●●●19:00
Tue 17 Aug 99%●●●●●●●●●●19:00
Wed 18 Aug 97%●●●●●●●●●●19:00
Thu 19 Aug 92%●●●●●●●●●●19:00
Fri 20 Aug 86%●●●●●●●●●●20:30
Sat 21 Aug 79%●●●●●●●●●●20:30
Sun 22 Aug 69%●●●●●●●●●●20:30
Mon 23 Aug 59%●●●●●●●●●●20:30
Tue 24 Aug 48%●●●●●●●●●●20:30
Wed 25 Aug 37%●●●●●●●●●●20:30
Thu 26 Aug 26%●●●●●●●●●●20:30
Fri 27 Aug 16%●●●●●●●●●●20:30
Sat 28 Aug 9%●●●●●●●●●●20:30
Sun 29 Aug 3%●●●●●●●●●●20:30
Mon 30 Aug 0%●●●●●●●●●●20:30
Tue 31 Aug 0%●●●●●●●●●●20:30

Check one night in detail Grand Cayman Bio Bay tours

Questions

What are the best nights to see the bioluminescence at Grand Cayman Bio Bay in August 2027?

The darkest nights are Sun 1 Aug, Mon 2 Aug, Tue 3 Aug, Wed 4 Aug, Thu 5 Aug, Sun 22 Aug, Mon 23 Aug, Tue 24 Aug, Wed 25 Aug, Thu 26 Aug and more. 17 of 31 nights score at least 4 out of 5.

Which nights should I avoid in August 2027?

Avoid the nights around the full moon on Tue 17 Aug, when moonlight washes out the glow.

19:00 or 20:30: which Grand Cayman Bio Bay tour is darker in August?

19:00 is the darker choice on 0 nights; 20:30 is the darker choice on 18 nights.

Grand Cayman Bio Bay darkness by month

Darkness score 1-5 per tour slot from twilight and moonlight. Weather and plankton health are not included. Times are local (America/Cayman).