Luminous Lagoon

Where the Martha Brae river meets the sea at Falmouth, fresh and salt water mix over a warm shallow bay, and the conditions suit bioluminescent dinoflagellates so well that the lagoon glows on essentially any dark night - a rarity among the world's glowing bays, most of which are seasonal or fickle. Boats head out after sunset, and every disturbance lights up: the wake behind the hull, a hand dragged through the water, fish darting away in streaks of blue-white. Guides usually let passengers swim, which is the part everyone remembers - your own body outlined in cold light.

What you actually see

• The glowing wake - the boat's trail lighting up on the way out.
• Swimming in the glow - the standard highlight of the evening trip.
• Fish trails - streaks of light as fish scatter beneath the boat.
• Falmouth's Georgian streets - the historic port town beside the lagoon.

When to go

The lagoon glows year round, which sets it apart from most bioluminescent bays. What matters is darkness - a moonless night is dramatically better than a full moon, and clouds help. Trips run nightly after sunset; book ahead in cruise season when ship passengers fill the boats.

Honest expectations

Photographs of glowing bays are almost always long exposures; the naked-eye reality is a soft blue shimmer, beautiful but subtler than the internet suggests. Bright moonlight can wash it out considerably. Operators vary - some run large noisy boats on tight schedules, others small quiet ones with proper swim time; ask which before booking. Bring a towel and expect to get in.

Nearby

Falmouth's Georgian town centre, Martha Brae rafting and the Montego Bay coast.