Sunset and Glowing Plankton

Some of the most memorable moments on Ko Lanta happen after the sun sets. This evening tour takes a small group out by boat in the late afternoon to a quiet part of the coast, where you watch the sky change color, eat a simple dinner or snack and then, once it is properly dark, slip into the water to see bioluminescent plankton light up around your hands and feet. The effect is a soft blue-green sparkle that follows every movement, and it is magical for children and adults alike. The trip is run by a local operator and is one of the highest-rated experiences on the island, popular with couples, families and anyone who wants something different from the usual day trips.

Bioluminescent plankton are tiny marine organisms that give off a flash of light when the water around them is disturbed. Ko Lanta is one of the places in Thailand where they appear regularly in the calm bays and mangrove-fringed waters, and the best displays happen on dark nights with no moon. Because of that, operators schedule these tours around the lunar calendar and the tide, and you may find that a bright moon makes the glow harder to see.

The guides will tell you honestly how strong the display is likely to be on the night, and it is worth asking when you book. Sightings are never guaranteed, since the plankton depend on water temperature, nutrients and recent weather, so treat the sunset as the sure thing and the glow as a bonus.

The format is relaxed. You are collected from your hotel in the afternoon, driven to the pier and taken by longtail boat to a quiet bay, where there is time to swim, snorkel or relax while the light fades. A simple meal or snack is usually served on the boat or the beach. As darkness falls the guide turns off the lights, and you enter the water slowly, moving your arms to stir the plankton.

Life jackets are provided and the water is shallow, which makes it safe for non-swimmers with the right equipment. Some versions use kayaks instead of swimming, and the paddle strokes light up the water in a trail of blue.

Practical advice will improve the experience. Wear a swimsuit and bring a towel, dry clothes, insect repellent and a waterproof torch if you like. Do not use sunscreen or lotions you do not want in the water, because they interfere with the plankton and the marine life.

Phones cannot capture the glow well, so enjoy it with your eyes rather than trying to photograph it. The return journey is made in the dark, so listen to the crew about boat safety and keep a light layer handy because the evening breeze can be cooler than you expect.

This is a lovely choice for couples, and it works for families with children who are comfortable in the water at night; check the minimum age with the operator. It is best in the dry season, from about November to April, when seas are calm and the sky is clear, and it suits any day when you want something quiet after a busy day of tours.

Pair it with a seafood dinner back at your hotel or in the old town, and plan a relaxed morning the next day, since the tour finishes late. If the weather turns, the crew may reschedule, so give yourself a spare evening.