Koh Ha
The diving highlight at Koh Ha is the series of fascinating caverns located at Koh Ha Yai, the largest island in the group. These caverns have large entrances and are safe to enter with appropriate training and supervision. You can surface inside a chamber and see ancient stalactites hanging from the cave ceiling. Sunrise is a magical time to dive here, as the sunlight filtering through the water creates a gorgeous emerald glow inside the chambers.
Another big attraction is the network of swim-throughs. You can access the main cave by entering the swim-through to the right of the main cavern entrance. Once through the entranceway, drop down a little. Then make a sharp left to squeeze out through the exit point. You will find yourself back in the main cavern's chamber. It is a short but exhilarating route.
Outside the caverns, Koh Ha's sloping reefs are covered in hard corals, sea fans, and anemones. Look for moray eels peering from crevices, octopus hunting across the rubble, and schools of snapper and fusilier moving above the reef. Nudibranchs are common here. So are clownfish in their anemones. Blacktip reef sharks patrol the channels, especially in the early morning and at dusk. For macro enthusiasts, the site rewards slow, patient diving. The limestone karst formations above the water are striking too. Between dives, you can take a moment to appreciate the sheer cliffs and turquoise lagoons. Thailand diving at Koh Ha combines geology, marine biology, and a touch of adventure.
Inside the lagoon between the islands of Koh Ha, a shallow sandy bottom sits at 5-10 metres. This is an excellent site for beginners, refresher dives, or a gentle third dive. The lagoon is sheltered from current. Visibility is good. You will find juvenile reef fish, small rays, and the occasional cuttlefish. It is also a great spot for snorkellers if you are travelling with non-divers.
The deep channel between Koh Ha Yai and Koh Ha Noi drops to over 40 metres. This is for advanced divers only. Current can run hard here. But the reward is pelagic action. Tuna, trevally, and barracuda hunt the channel. Reef sharks patrol the drop-offs. Whale sharks pass through on occasion, usually between February and April. Your dive guide will assess conditions before attempting a dive here.
Koh Rok
The west side of Koh Rok is dominated by a hard coral reef that slopes gently downward. The coral here is healthy and dense. Schools of colourful reef fish hover above the reef crest. Below, plenty of moray eels hide in the crevices. Octopus hunt across the sandy patches. Look closely for the numerous different nudibranch species. They come in bright colours and unusual shapes. Blacktip reef sharks are common in the early morning and again at dusk. Watch out for Kuhl's blue-spotted stingrays partially hidden in the sand on the seabed. This is the most common ray found at Thailand dive sites. They are shy. Approach slowly for a good look.
On the eastern side of Koh Rok, the character changes. Soft corals dominate. Large gorgonian fans and sponges cover the reef. This attracts plenty of turtles. Green and hawksbill turtles feed on the sponges and algae. You can get quite close to them, especially while they are eating. Respect their space. Do not chase. If you stay still, they will often swim towards you.
The southern point of the island has fairly strong current when the tide runs. Pelagic fish are often seen here, including mackerel, cobia, and the occasional tuna. Barracuda patrol the edge of the reef. Reef sharks pass through. This is a good spot for a drift dive if the current is running. Your dive guide will advise.
Between dives, Koh Rok offers stunning white sand beaches and shallow snorkelling areas. The island is uninhabited, protected, and quiet. For divers looking to experience diving in Thailand without the crowds of the Similans or Phi Phi, Koh Rok is a genuine gem.
