How and where to see bioluminescent (glowing) plankton in Krabi

One of the most unique things to do in Krabi after dark? We think that a night time search for the glowing plankton should be high on your list! Known as bioluminescent plankton, these tiny organisms light up the water with a magical blue-green glow when disturbed. It’s a rare natural sight that (in our experience) can still surprise even the most seasoned travellers.

The best way to spot glowing plankton in Krabi is on one of the night boat tours from Ao Nang, Railay or Krabi Town. While they sometimes show up near the beach, it’s much clearer out at sea (we’ve been taking people out on our plankton tour from Ao Nang for over a decade, and it’s safe to swim out there!)

We’d previously written a more general blog about the luminescent plankton: Explorer la beauté et la science du plancton bioluminescent. This covered the science behind the “sea sparkle”, alongside the different types, their role in the food chain, and the effect that climate change is having on them.

However, to help you plan a more specific experience and highlight the best Krabi tours for night swimming with plankton, here are the top questions people ask about bioluminescent plankton in Krabi – answered by our team of guides who head out to swim alongside it almost every night!

Where can I see bioluminescent plankton in Krabi?

You can often see bioluminescent plankton near Railay Beach, Tonsai Beach, and on night tours around the Hong Islands. The glow is best visible in dark, calm waters, away from light pollution. Most people take an sunset/evening boat tour from Ao Nang or Railay to reach the good spots. Occasionally, the plankton can be seen from the shore (however, it’s usually more vivid in deeper water.)

When is the best time to see bioluminescent plankton in Krabi?

The best time is during new moon periods, when the sky is darkest. If you can, avoid full moons, as the brightness can wash out the glow. However, don’t be disheartened if you’re short on time and can’t avoid the bigger moon. Our tour guides know the best dark spots, shaded by the looming limestone cliffs (making sure you can still see the sparkle.)

Calm, clear nights are ideal, and sightings are most common between May and November, though they do occur year-round. Specific bioluminescent plankton tours usually start after sunset, but local companies (like us) include the experience as part of a wider afternoon sunset tour so that you get more out of your day.

We find that conditions like warm water, low wind, and no rain also improve visibility.

Are there bioluminescent plankton tours in Krabi?

Yes (and no). We’re not aware of any tours that go out specifically for the glowing plankton – even though there are a few operators who market themselves specifically as that (leaving from Ao Nang, Railay, and Krabi Town.) When you dig down into the details of these boat tours, you’ll find that they all incorporate island hopping and sunset dinners beforehand, with the chance to swim among the plankton after dark.

If you want a tour in Krabi that focuses specifically on the plankton experience, you are better negotiating a private longtail ride with the boatmen or tour operators. With this, you can dictate where you go and how long you go out for.

From our experience, the later can sometimes be a little underwhelming. Many guests don’t want to jump into the waters after dark, choosing to view the glow from above. It’s worth noting that (while you can see them this way) the real experience comes from getting into the water with the snorkel mask.

Is it safe to swim with bioluminescent plankton in Krabi?

Yes, it’s generally safe to swim with bioluminescent plankton in Krabi. The plankton itself is harmless and non-stinging. Our boat takes you to calm waters where it’s safe to swim under supervision. Everyone is provided with a life jacket for extra safety, and our guides use torches to highlight the best areas and keep a vigilant eye on swimmers.

That said, if you head out with a different tour company, always follow your guide’s instructions and be cautious if you’re not a confident swimmer. Avoid touching coral or wildlife, and don’t swim if there are strong currents or storms.

How can I photograph bioluminescent plankton in Krabi?

Photographing bioluminescent plankton is tricky because the glow is faint and only visible in complete darkness (our guides have been using GoPro’s and other waterproof tools for years and are still yet to capture images worthy of their own Instagram post!) Many of the images you see on tour websites are digitally enhanced or (unfortunately) AI images – the light from the small tiny organisms is difficult to photograph.

If you’re determined to try and photograph them, we recommend using a camera with manual settings, long exposure, high ISO, and a tripod or very steady hand. Camera phones usually can’t capture it well unless they have a night mode and low-light capabilities (and even then, it doesn’t ever capture the light in the same way in which you experience it in person.)

What causes bioluminescent plankton in Krabi to glow?

Ok, here’s the science …

The glow comes from microscopic organisms called dinoflagellates, a type of plankton that produces light when disturbed. This natural reaction, called bioluminescence, is a defence mechanism. When the water is moved (by swimming, waves, or even splashing) the plankton emits a soft blue or green light. It’s not unique to Krabi, but our region’s warm, calm, and relatively dark waters make it easier to see.

Can I see bioluminescent plankton from the beach in Krabi or do I need a boat?

While it’s possible to see plankton from the beach, it’s much more visible and reliable if you go out by boat. Light pollution and shallow water often reduce the glow near shore. Tonsai and Railay (especially Railay’s West Beach) occasionally have visible plankton on the beach after dark, but for the clearest experience, a night tour to less-populated islands or deeper water would be our go-to advice.

Interested in seeing it for yourself?

Booking a spot on our 4 Croisière cocktail au coucher du soleil sur l'île + plongée avec masque et tuba la nuit is one of the most memorable ways to see the glowing plankton (and experience the Thai coastline by night.) Even if you’re not a strong swimmer (or can’t swim at all), we’ve got you covered – our crew supply life rings, paddleboards, and in-water assistance to even the most nervous or inexperienced of swimmers.

Our boat is spacious, with comfy cushions on the deck and rooftop, giving you plenty of space to relax, take in the views, and personalise your trip. While you’re relaxing, enjoy our free-flowing drinks and snacks, plus a cocktail bar where you can sip your favorite mix.