Scuba Diving at Koh Haa

Diving at Koh Haa

Koh Haa means "Five Islands" in Thai (there are actually six, but no one's counting), and the cluster sits around 16 to 25 km west of Koh Lanta (operator sources differ on exact distance) inside Mu Ko Lanta National Park. It's the most beginner- and intermediate-friendly destination in the southern Andaman: sheltered, varied terrain, reliably good visibility, and one of the cleanest cavern dives in Thailand. You can run an Open Water training session in the Lagoon at 08:30, dive the Cathedral cavern after lunch, and finish on a wall dive with hawksbill turtles and ghost pipefish before the boat heads home.

The water sits at 27 to 30 °C (81 to 86 °F) and visibility holds at 20 to 30 m (66 to 98 ft) through the high season, often better than nearby Phi Phi sites because Koh Haa sees less boat traffic. Currents are gentle on most of the cluster, picking up only between islands and on the outer western pinnacles. The Cathedral on Koh Haa Yai is the trademark dive: a twin-cavern complex with an air dome you can surface inside, shafts of natural light from below-water entrances, and stalactites overhead. It's a cavern, not a cave, so daylight is always visible and no special certification is required.

The islands themselves are uninhabited, so you'll need to base on Koh Lanta or Phi Phi. Lanta is closer (about an hour by speedboat) and has more dive operators, but Phi Phi-based day boats reach Koh Haa in around 90 minutes to 2 hours. The marine park closes from 16 May to 31 October every year, and most dive shops close with it. The window is November through April.

Top dive sites at Koh Haa

The top dive sites at Koh Haa cover six small islands with caverns, walls, swim-throughs, and a sheltered training lagoon. Most operators run a 2- or 3-dive itinerary that mixes the headline Cathedral with one beginner-friendly site and one wall.

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The Cathedral (Koh Haa Yai)

The Cathedral is Koh Haa's headline dive. Two large connected caverns sit inside Koh Haa Yai (#5, "the big one"), with entrances at around 12 m (39 ft) and chambers stretching back to roughly 18 m (59 ft). Inside, you can surface into an air dome and look up at stalactites poking down from the limestone ceiling, while below-water entrances send shafts of natural light through the chambers. Glassfish, lionfish, and sweepers fill the cavern interior. It's a true cavern dive (daylight is always visible, no overhead training required), but good buoyancy is mandatory because silt-up is a real risk.

• Depth: 12–30 m (40–98 ft); surrounding wall to 35 m (115 ft)
• Visibility: 20–30 m (66–98 ft)
• Current: Gentle inside the cavern complex
• Level: Open Water with good buoyancy under a guide; Advanced recommended
• Key species: Glassfish, lionfish, scorpionfish, sweepers, hawksbill turtle (outside)

The Chimney (Koh Haa Neua)

The Chimney is a vertical swim-through on the west corner of Koh Haa Neua (#1, the northernmost island). Operators run it in either direction: you either drop in at 4 to 5 m (13 to 16 ft) and exit through a chute that bottoms out around 17 m (56 ft), or descend to 17 m (56 ft) first and ascend up through the chimney. Either way, a vaulted rock chamber sits at the midpoint around 8 to 9 m (26 to 30 ft). The dive then continues along a wall and boulder field. Bronze cave sweepers school inside the chute, and the boulders around the exit hold seahorses, frogfish, and painted spiny lobster.

• Depth: 4–18 m (13–60 ft) through the swim-through; deeper on the wall
• Visibility: 20–30 m (66–98 ft)
• Current: Gentle to mild
• Level: Open Water with solid buoyancy; Advanced recommended
• Key species: Bronze cave sweepers, seahorses, frogfish, painted spiny lobster

Koh Haa Lagoon

The Lagoon is the sheltered bowl of water between Koh Haa Song (#2), Sam (#3), and Si (#4). The bottom is white sand at 5 to 15 m (16 to 49 ft) with hard coral patches around the edges. It's the most-used Open Water training site in the area, doubles as a safety-stop and surface-interval spot, and is a known tigertail seahorse location. Snorkellers and Discover Scuba beginners share the water with experienced divers running shore-side macro hunts.

• Depth: 5–15 m (16–49 ft)
• Visibility: 20–30 m (66–98 ft)
• Current: Consistently calm
• Level: Open Water students, Discover Scuba, snorkellers
• Key species: Tigertail seahorse, ghost pipefish, garden eels, juvenile reef fish

Koh Haa Yai West Wall & Koh Haa #6

The west side of Koh Haa Yai drops into a wall with boulder fields, sea fans, and barrel sponges. The small pyramid-shaped islet known as Koh Haa #6 sits just off Yai and provides swim-throughs around its pinnacle. The terrain mixes mild current with reef life: schooling fusiliers and snapper, hawksbill turtles working the boulders, and the occasional blacktip reef shark cruising past at depth.

• Depth: 5–30+ m (16–100+ ft)
• Visibility: 20–30 m (66–98 ft)
• Current: Mild, picking up between islands
• Level: Open Water (Advanced for deeper sections)
• Key species: Hawksbill turtle, schooling fusilier, schooling snapper, blacktip reef shark, Kuhl's stingray

Koh Haa Neua West Wall

The north side of Koh Haa Neua drops vertically along its west and east faces, sloping more gently on the north and south. The channel between islands runs past 50 m (164 ft). Mild current along the wall sometimes brings pelagic action, and the "Secret Garden" pocket (variously placed on the south side or between Neua and Koh Haa Song) is a known hawksbill turtle spot. Leopard sharks turn up occasionally on the sand bottom: not a signature here, but a possibility.

• Depth: 5–30+ m (16–100+ ft)
• Visibility: 20–30 m (66–98 ft)
• Current: Mild to moderate, depending on the channel
• Level: Open Water (Advanced for the deeper wall)
• Key species: Hawksbill turtle, leopard shark (occasional), blacktip reef shark, schooling barracuda, Kuhl's stingray

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Best time to dive Koh Haa

The best time to dive Koh Haa is November through April, when the Andaman is flat, visibility regularly hits 30 m (98 ft), and Mu Ko Lanta National Park is open. The park closes from approximately mid-May through October, and most dive operators close with it.

Koh Haa is one of the most forgiving dives in the country, so the season's shoulders (November, early May before closure) deliver good diving at slightly lower prices. February through April remains the strongest window.

Diving conditions

Diving conditions at Koh Haa are the gentlest in the southern Andaman. Most of the cluster is sheltered by the islands themselves, currents are mild, and the Lagoon is calm enough to teach in. Outer pinnacles and the channels between islands can pick up.

Marine life at Koh Haa

Marine life at Koh Haa is heavy on macro and reef variety rather than big-animal headliners. The Lagoon turns up tigertail seahorses, ghost pipefish, frogfish, and garden eels. The walls and reef slopes deliver hawksbill turtles, schooling fusiliers and snapper, the occasional leopard shark, and blacktip reef sharks at depth.

Tigertail seahorse: year-round, especially around Koh Haa Lagoon

The Lagoon is a known tigertail seahorse spot. They sit motionless on sea fans and rubble at 8 to 14 m (26 to 46 ft), and guides know the regular hangouts. Buoyancy matters here. Sand stir-up ruins the photograph and the rest of the dive.

Frogfish and ghost pipefish: November to April, especially around Koh Haa Neua

Frogfish (including occasional clown frogfish) and ornate ghost pipefish show up around the boulder fields below The Chimney and on the walls of Koh Haa Yai. Slow it down on the descent. These are find-it-yourself critters that reward divers who actually look.

Hawksbill turtles: year-round, especially around Koh Haa Yai West Wall

Hawksbills work the boulder fields and reef slopes, particularly on the west side of Koh Haa Yai and in the "Secret Garden" pocket of Koh Haa Neua's south wall. They're regulars, not bonuses.

Beyond the macro list, you'll find the full reef cast: schooling fusiliers, snapper, batfish, barracuda; large moray eels in the boulder fields; surgeonfish, parrotfish, angelfish, butterflyfish, and damselfish across the shallows. Whale sharks pass through during the high season but treat them as luck rather than expectation. Leopard sharks turn up on the sand bottom occasionally; for reliable leopard shark sightings, you'll do better at Hin Bida or Koh Bida Nok.

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Practical information

Dive prices at Koh Haa

• 2-tank day trip from Koh Lanta: THB 3,000 – 3,200 (USD 85 – 95), including gear, guide, lunch and drinks
• 2-tank day trip from Koh Phi Phi: Typically THB 3,200 – 3,800 (USD 90 – 110)
• Marine park fee: Mu Ko Lanta National Park entry is THB 200 for foreign adults; many operators add a diver surcharge that brings the total to around THB 600 per diving day, paid in cash on the boat
• PADI Open Water course (often run partially at Koh Haa Lagoon): THB 14,000 – 16,500 (USD 400 – 475)

Getting to Koh Haa

Koh Haa has no accommodation, so you'll base elsewhere and day-trip in.

From Koh Lanta: speedboats from Saladan Pier take 45 minutes to an hour. Longtail snorkel boats take around 80 minutes. This is the most common access and the cheapest.

From Koh Phi Phi: 90 minutes to 2 hours by speedboat. Day boats typically run 07:00 to 16:00 itineraries.

From Phuket: usually via combined long day trip or as part of a southern Andaman liveaboard.

Most dive operators on Lanta cluster in Saladan, with a few more on Long Beach. On Phi Phi Don, dive shops are clustered around Tonsai village. Day boats leave between 07:00 and 08:00 and return mid-to-late afternoon.

Hyperbaric chamber

The nearest recompression facility is the SSS Phuket Hyperbaric Chamber at Bangkok Hospital Siriroj (multiplace, 24/7), the first chamber in southern Thailand and still the regional reference. From Koh Haa the realistic transfer is 4 to 6 hours by road and ferry via Lanta or Phi Phi, or faster by air ambulance via Krabi.