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AdventureNight tour · Cat Ba

Bioluminescent plankton in Lan Ha Bay: when to go and which tour

The bioluminescent plankton of Cat Ba and Lan Ha Bay glows blue-green when you move through the water, best on dark, calm nights in the warm months. It is never guaranteed: time your night around the new moon and pick a tour that goes far from the lights.

On the chart

Lan Ha lagoons (approximate)

Season
Warm months, roughly May to October
Best nights
Moonless, calm nights around the new moon
Where
Dark lagoons of Lan Ha, away from Cat Ba town
Tours start
Cat Ba town or Ben Beo pier, late afternoon
Platform prices
From $37 per person on GetYourGuide
Direct prices
From 1,500,000 VND (kayak by day, plankton by night)
Guaranteed?
No: brightness changes from night to night

Updated October 16, 2026Facts checked against official sourcesContains affiliate links

Glowing plankton: what you can book

9 options · Prices checked on October 16, 2026

Length

See everything on GetYourGuide →See everything on Klook →

Bioluminescent plankton is one of the reasons people stay a night on Cat Ba rather than seeing Lan Ha Bay only from a cruise ship. Microscopic plankton, mostly dinoflagellates, flash blue-green when the water around them is disturbed: a paddle stroke, a hand trailed from a boat, a swimmer's kick. On a good night every movement leaves a trail of sparks. On a poor night you see a faint shimmer, or nothing.

The tours are short evening trips from Cat Ba town, usually combined with a sunset and dinner on the water. This page covers when the glow is strongest, how the tours work, what they cost, and the rules that now limit night kayaking in Lan Ha (vịnh Lan Hạ).

When to see bioluminescent plankton in Lan Ha Bay

Three things decide whether you see it: the season, the moon and the light around you.

Season. The glow is a warm-water event. In winter it is rare and weak. Sources put the best window anywhere from May–August to May–October, so plan for the warm months, roughly May to October, and keep your expectations modest at either end.

Moon. Pick dark, moonless nights. A full moon can wash the glow out completely. The best week is around the new moon, which falls at the very start and end of each lunar month. The next dark nights are below.

Darkest nights for the glowing plankton
Best windowNew moonFull moon (weakest)
Nov 7 – Nov 13Nov 10Nov 24
Dec 6 – Dec 12Dec 9Dec 24
Jan 5 – Jan 11Jan 8Jan 23
Feb 3 – Feb 9Feb 6Feb 21
Mar 5 – Mar 11Mar 8Mar 23
Apr 3 – Apr 9Apr 6Apr 21
May 3 – May 9May 6May 21
Jun 1 – Jun 7Jun 4Jun 19
Jul 1 – Jul 7Jul 4Jul 19
Jul 30 – Aug 5Aug 2Aug 17
Aug 29 – Sep 4Sep 1Sep 16
Sep 28 – Oct 4Oct 1Oct 15
Oct 27 – Nov 2Oct 30Nov 14
Nov 26 – Dec 2Nov 29Dec 13

The glow shows best on moonless, calm nights; it is never guaranteed. Dates in Vietnam time.

Light and calm water. Town lights, the floodlights of big cruise ships and the lamps of squid-fishing boats all kill the effect. Calm water helps too. That is why the good tours head for a dark lagoon well away from Cat Ba town, and why a plankton night is hard to combine with the squid fishing on a big cruise ship.

How a Cat Ba plankton tour works

Plankton trips leave from Cat Ba town or Ben Beo pier (bến Bèo, "bến" means pier), about 2 km from town, in the late afternoon. The typical shape is a sunset on the water, dinner on a boat or at a floating farmhouse, then the dark part of the evening at a lagoon, back by about 21:00.

A typical evening plankton tour from Cat Ba

  1. Hotel pickup in Cat Ba townSome tours start at 16:00 with a longer sunset paddle

  2. Local boat from Ben BeoSunset on the way out

  3. Dinner with fishermen at a floating farmhouseSome tours serve a barbecue on board instead

  4. Guided night paddle to a dark spotWhere the plankton shows

  5. Back to the floating houseThen the boat to Ben Beo

  6. Boat back to Ben Beo, transfer to your hotel

That schedule follows Blue Swimmer's published evening tour from Beo harbour. Cat Ba Ventures runs a "sunset and night kayaking with bioluminescent plankton" trip from 16:00 to 20:30. Both include a guide and transfers in town.

Cat Ba town1Ben Beo pier2Cai Beo fishing village3Lan Ha lagoons (approximate)4Van Boi5Monkey Island (Cat Dua)6
  1. 1Cat Ba townTownDirections ↗
  2. 2Ben Beo pierPierDirections ↗
  3. 3Cai Beo fishing villageVillageDirections ↗
  4. 4Lan Ha lagoons (approximate)SightDirections ↗
  5. 5Van BoiBeachDirections ↗
  6. 6Monkey Island (Cat Dua)SightDirections ↗
Diamonds: piers; circles: sights and villages; arches: caves; circles with a wave: beaches; triangles: peaks. · Chart: © OpenStreetMap contributors

Kayaking rules: what that means for plankton tours

Every plankton tour on sale depends on night kayaking or swimming, and that is where the rules bite. Kayaking in the Cat Ba bays has been under an official suspension since Nov 2024, re-confirmed in late 2025. Some ships offer it only in a designated area or replace it with a bamboo boat, tender or swim. Ask the operator in writing.

The original order was reported by VnExpress. No notice lifting it has been published, yet Cat Ba operators still sell night kayak tours. Travel sources also say local authorities occasionally restrict night boating. In practice:

  • Ask the operator in writing whether the kayak part actually runs on your date, and what replaces it if it does not (a swim from the boat or watching from a small boat).
  • Expect a life jacket for the whole trip. Since June 2026 Cat Hai Special Zone (đặc khu Cát Hải, the local authority) requires every passenger on Lan Ha boats to wear a certified life jacket from boarding (Tiền Phong).
  • Swimming at night in a lagoon is only for confident swimmers, and only with the guide's go-ahead.

More on the suspension and where paddling is still offered on kayaking in Lan Ha Bay.

Plankton tour prices: GetYourGuide vs booking direct

On GetYourGuide, Cat Ba plankton tours start at $37 per person, and most of the well-reviewed ones cost about $44. The most reviewed is the Lan Ha Bay plankton boat tour from Cat Ba ($44, 4.8 from more than 600 reviews); a sunset and night kayak tour is also $44.

Booking direct in Cat Ba town, prices are in VND:

Operator and tour Direct price
Cat Ba Climbing: kayak by day, plankton by night 1,500,000 VND
Cat Ba Climbing: deep water solo, then plankton kayak 2,000,000 VND
Cat Ba Climbing: climbing at Moody Beach and night plankton kayak 2,480,000 VND
Cat Ba Climbing: day trip from Hanoi with deep water solo and plankton 3,800,000 VND (min 2; 4,600,000 solo)
Blue Swimmer: sunset and evening plankton kayak Not published
Cat Ba Ventures: sunset and night plankton kayak Not published

The direct combos are longer days built around a second activity; the platform tours are evening-only trips. If you only want the plankton, the $37–48 GetYourGuide tours are the simpler buy, with free cancellation on many listings, which matters for a weather-dependent night. Compare the rock climbing and deep water solo page if you want to pair the evening with a climbing day.

See everything on GetYourGuide →See everything on Klook →Prices checked on October 16, 2026

Plankton on an overnight cruise

A few overnight products build the plankton into the trip. Venezia, whose small boats leave from Ben Beo, sells a 2D1N variant with night kayaking among bioluminescent plankton; see the Venezia review. Cat Ba Expedition's 2D1N small cruise (4,300,000 VND per guest) lets you choose an evening plankton kayak or squid fishing. On GetYourGuide, several 2D1N trips include a plankton excursion, from about $105.

Big cruise ships from Tuan Chau are a poor bet for plankton. Their own lights and the lamps used for squid fishing are exactly the conditions that hide the glow. If plankton matters, choose a small boat from Cat Ba or a dedicated evening tour, and compare with our 2 days 1 night cruise guide.

Our plankton picks

1

First-timers who want the most-reviewed tour

Boat-based plankton tour from Cat Ba with a strong rating from more than 600 reviews. Ask how the evening runs if kayaking is off on your date.

2

Sunset plus a night paddle

Starts with a sunset kayak and stays out after dark. Check that it heads for a dark lagoon away from town.

3

Coming from Hanoi or staying on Cat Ba

Sunset and plankton evening that can be booked with a Hanoi connection. Read the transfer details carefully.

Getting to Cat Ba for a night tour

Plankton tours start in the evening on Cat Ba Island, so you need to sleep there. The car ferry from the Cat Hai piers (Dong Bai, formerly Got) to Cai Vieng stops in the early evening: from 1 September 2026 the last boat leaves Cat Ba at 17:30. There is no road bridge, so there is no way back to the mainland after the tour.

The easy route is a combined bus and ferry ticket from Hanoi to Cat Ba town: about 3–3.5 hours, from USD 11 (USD 15 by limousine van, called xe limousine locally). Details on how to get to Lan Ha Bay and what else to do on the island in our Cat Ba Island guide.

Weather and safety in plankton season

The plankton months overlap with the wet season and the storm season. May to September each bring over 200 mm of rain, August is the wettest, and storms are possible from June to November. When the authorities issue a sea ban, all boats stay in port, including evening tours, and ferries to and from Cat Ba stop. In August 2026 more than 1,700 tourists were stranded on Cat Ba during one storm. Keep a buffer day before an onward flight.

On board: wear the life jacket the whole time and keep your phone and valuables in a dry bag. See the best time to visit for the full climate picture.

FAQ

When is the best time to see bioluminescent plankton in Cat Ba?

In the warm months, roughly May to October, on dark, moonless and calm nights. The week around the new moon is best; a full moon can wash it out.

Is bioluminescent plankton in Lan Ha Bay guaranteed?

No. It is a natural event and its brightness changes from night to night, even in season. Book a tour with free cancellation and, if you can, keep a second night on Cat Ba.

How much does a plankton tour in Cat Ba cost?

Evening tours on GetYourGuide start at $37 and most cost about $44 per person. Direct combos in Cat Ba town start at 1,500,000 VND for a kayak day with a plankton evening.

Can you kayak at night in Lan Ha Bay?

Kayaking in the Cat Ba bays has been under an official suspension since November 2024, re-confirmed in late 2025, although operators still sell night kayak tours. Ask the operator in writing whether the kayak part runs on your date and what replaces it.

Can I see the plankton from a Ha Long cruise ship?

Rarely. Ship lights and squid-fishing lamps hide the glow. A small boat or evening tour from Cat Ba heads for darker water.

Can I photograph the glowing plankton?

Phone cameras usually cannot capture it. The bright images online are long exposures taken with a tripod.

Keep exploring

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