HTMS Hanhak Sattru Wreck
Marine life at HTMS Hanhak Sattru Wreck...
Situated along the quiet eastern coastline of Koh Tao, this dive blends relaxed reef scenery with a Thai Navy wreck sank on Koh Tao in 2022. Aow Mao Bay slopes down along the coast making some interesting landscape before reaching around 18–20 meters, where the HTMS Hanhak Sattru rests upright on the seabed at approximately 20–24 meters. The gradual depth change makes for an easy, flowing dive profile with plenty to see from start to finish.
Currents & Conditions
Typically sheltered from stronger offshore weather, Aow Mao Bay often enjoys calm surface conditions and comfortable diving. Visibility generally ranges between 8–20 meters — slightly more variable than outer pinnacles but often excellent for spotting macro life. Water temperatures remain warm at 27–30°C, making this a very relaxed dive environment.
Underwater Landscape & Marine Life
This is a dive of contrasts — purposeful structure blending seamlessly into calm natural reef. Your adventure begins with a descent onto the HTMS Hanhak Sattru, its silhouette emerging from the blue as you approach. Now evolving into a thriving artificial reef, the wreck is increasingly alive with fusiliers, snapper, and reef fish swirling around its frame. Look carefully along the hull and you may spot lionfish hovering beneath ledges, moray eels tucked into shadows, and groupers confidently patrolling their new territory, while the surrounding seabed often reveals rays and other well-camouflaged bottom dwellers. Leaving the wreck behind, you’ll gradually ascend along the sloping reef of Ao Mao, where the atmosphere shifts from dramatic structure to relaxed bay diving. Coral patches, sea whips, and sandy channels create the perfect habitat for blue-spotted stingrays, frequently seen resting on the seabed. Juvenile reef fish thrive among the rocks, attracting passing predators such as trevally and barracuda that occasionally sweep through the area from out of nowhere. Less crowded than many headline sites, this dive often feels peaceful — ideal for divers who enjoy slowing down, extending their bottom time, and truly observing the underwater world.
Skill Level & Certification
Suitable for Open Water divers thanks to the manageable depths and typically gentle conditions. Advanced divers will also appreciate the wreck element and the chance for longer, more exploratory dive routes.
Access & Logistics
This is an East coast dive which means we start our journey with a taxi ride to Hin Wong Pier where we meet our shuttle boat to take us to the dive boat. We go here during the June to September Southwest monsoon so a 20 minute trip from Hin Wong in the shelter of the island makes this an ideal morning adventure with minimal travel time and maximum bottom time. We meet at 7:20am and typically return by 12:30pm. The trip includes one combined dive exploring both Aow Mao Bay and the Wreck, followed by a second dive at another nearby site selected based on the day’s conditions — ensuring a varied and rewarding morning underwater.
