The glow worms

Tonight, from about 7:32 — roughly twenty minutes, in the shallow bays and channels.

The glow worms keep to the moon — the third, fourth and fifth night after a full one. The females rise and give off a green light, and the males follow it. (Odontosyllis enopla, if you want to look them up.)

Why those nights: the moon rises later each evening after it is full, so on all three it is still below the horizon while this happens — the water is the brightest thing out there. The window grows each night: 175 minutes of darkness before moonrise.

Knowable

the nights, the time, that the sky will be dark, and roughly how long it lasts.

Luck

the tide — an ebbing one helps and there is no tide gauge in the Turks & Caicos, so nobody predicting it here is reading one. Also cloud, and how many rise. Sightings are never guaranteed.

Two boats make a trip of it.

• Sun Charters — a 70ft sailing boat that has worked these waters since 1998.
• Ocean Vibes — sunset, glow worms and stargazing on a sailing catamaran.

Other operators may go out on these nights; worth asking.