Koh Ha

Koh Ha is an advanced dive destination in the Andaman Sea that offers diverse underwater exploration around a group of small limestone islands south of Koh Lanta. With depths reaching thirty meters and features ranging from caverns to walls to coral gardens, this site provides some of the most varied and spectacular diving in the Krabi-Lanta region. The limestone islands of Koh Ha create a dramatic above-water setting of vertical cliffs and tropical vegetation, and the underwater landscape continues this geological drama. The walls plunge from the waterline into deep blue water, their surfaces decorated with colorful marine growth. The most celebrated feature is a large underwater cavern known as The Cathedral, where divers can enter a spacious chamber with crystal-clear water, air pockets at the ceiling, and stalactites that testify to the cave's origins above sea level. The reef systems around the islands are in excellent condition. Hard coral diversity is outstanding on the shallower reef flats, while the deeper walls host spectacular displays of soft corals, sea fans, and barrel sponges. The overall reef health reflects the benefits of the site's relative isolation and the limited diving pressure compared to busier destinations. Marine encounters at Koh Ha include a wide range of species. Leopard sharks rest on the sandy flats, reef sharks patrol the wall edges, and turtles feed on the healthy sponge communities. The fish population is dense and varied, with schooling species providing mid-water spectacle and the reef communities offering constant color. Macro life is rich, with nudibranchs, seahorses, and ghost pipefish found by dedicated searchers. Koh Ha delivers one of the most complete diving experiences in Thailand, combining geological spectacle, pristine reef health, exciting marine encounters, and the adventure of cavern exploration. For advanced divers visiting the Koh Lanta area, these limestone islands are an essential destination that showcases the very best of Andaman Sea diving.