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Grand Cayman Bio Bay in July 2027: darkest nights

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

14 pitch-dark nights, 17 dark nights

New moon Sat 3 Jul · Full moon Sun 18 Jul

Night by night, July 2027

NightMoon19:0020:30Best
Thu 1 Jul 5%●●●●●●●●●●20:30
Fri 2 Jul 1%●●●●●●●●●●20:30
Sat 3 Jul 0%●●●●●●●●●●20:30
Sun 4 Jul 2%●●●●●●●●●●20:30
Mon 5 Jul 6%●●●●●●●●●●20:30
Tue 6 Jul 13%●●●●●●●●●●20:30
Wed 7 Jul 22%●●●●●●●●●●20:30
Thu 8 Jul 32%●●●●●●●●●●20:30
Fri 9 Jul 43%●●●●●●●●●●20:30
Sat 10 Jul 54%●●●●●●●●●●20:30
Sun 11 Jul 65%●●●●●●●●●●20:30
Mon 12 Jul 74%●●●●●●●●●●20:30
Tue 13 Jul 83%●●●●●●●●●●20:30
Wed 14 Jul 90%●●●●●●●●●●20:30
Thu 15 Jul 95%●●●●●●●●●●20:30
Fri 16 Jul 98%●●●●●●●●●●19:00
Sat 17 Jul 100%●●●●●●●●●●19:00
Sun 18 Jul 100%●●●●●●●●●●20:30
Mon 19 Jul 98%●●●●●●●●●●20:30
Tue 20 Jul 94%●●●●●●●●●●20:30
Wed 21 Jul 89%●●●●●●●●●●20:30
Thu 22 Jul 82%●●●●●●●●●●20:30
Fri 23 Jul 74%●●●●●●●●●●20:30
Sat 24 Jul 64%●●●●●●●●●●20:30
Sun 25 Jul 54%●●●●●●●●●●20:30
Mon 26 Jul 43%●●●●●●●●●●20:30
Tue 27 Jul 33%●●●●●●●●●●20:30
Wed 28 Jul 22%●●●●●●●●●●20:30
Thu 29 Jul 14%●●●●●●●●●●20:30
Fri 30 Jul 7%●●●●●●●●●●20:30
Sat 31 Jul 2%●●●●●●●●●●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 July 2027?

The darkest nights are Thu 1 Jul, Fri 2 Jul, Sat 3 Jul, Sun 4 Jul, Mon 5 Jul, Fri 23 Jul, Sat 24 Jul, Sun 25 Jul, Mon 26 Jul, Tue 27 Jul and more. 17 of 31 nights score at least 4 out of 5.

Which nights should I avoid in July 2027?

Avoid the nights around the full moon on Sun 18 Jul, when moonlight washes out the glow.

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

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