Koh Sii

Koh Sii is a beginner-friendly dive site in the Andaman Sea near Krabi, a small island whose surrounding reefs offer accessible and enjoyable diving in the warm waters of Thailand's stunning Krabi coastline. The site provides an excellent introduction to Andaman Sea diving for newer divers, with gentle conditions, moderate depths, and the rich marine life that characterizes the limestone island environments of this region. The island sits among the karst formations that make the Krabi seascape so visually dramatic, both above and below the water. These limestone islands, formed over millions of years and sculpted by tropical erosion, create underwater habitats of caves, overhangs, and textured rock surfaces that support diverse marine communities. The sheltered waters between the islands provide calm conditions that are ideal for beginner-level diving. The reef around Koh Sii features a mix of hard and soft corals growing on the limestone substrate. Brain corals, massive Porites heads, and various branching species form the hard coral component, while soft corals and small sea fans add color and movement. The limestone surface is naturally pitted and irregular, providing countless attachment points for marine organisms and creating the micro-habitats that support biodiversity far greater than what smooth rock could sustain. Fish life is typical of the Krabi area's healthy reef systems. Schools of damselfish hover above the coral heads, while wrasse species cruise the reef in their colorful livery. Parrotfish and surgeonfish maintain the reef's ecological balance through their feeding activities, and the rocky overhangs shelter groupers, sweetlips, and the occasional sleeping turtle. The sandy patches between reef sections harbor stingrays and gobies. The macro life at Koh Sii rewards patient observation. The limestone crevices are home to shrimp, crabs, and the nudibranchs that have made Andaman Sea diving a macro photographer's delight. Anemones host their resident clownfish families, and the interaction between these symbiotic partners provides endless entertainment for divers of all experience levels. Visibility around the island is generally good during the diving season from November through April, when the Andaman Sea enjoys calm conditions and clear water. The proximity to Krabi's mainland coast means the site is accessible for day trips and half-day excursions, making it a convenient option for divers staying in the Ao Nang, Railay, or Krabi Town areas. Koh Sii offers a relaxed and rewarding introduction to the underwater world of Krabi's limestone islands. The combination of easy conditions, healthy reef ecosystems, and the stunning tropical scenery both above and below the waterline creates a dive experience that captures the essence of Andaman Sea diving at its most welcoming.