HTMS Hanhak Sattru Wreck, Koh Tao: dive a recent fast attack craft

The HTMS Hanhak Sattru, hull number 312, is one of Koh Tao's newer wreck sites, purpose-sunk in September 2023 near Mao Bay. This vessel is a fast attack craft, identical in class to the HTMS Suphairin, providing a similar exploration profile for divers familiar with that wreck. You approach a 45-metre long steel hull, sitting upright and slowly being colonized by marine life, an excellent example of how artificial reefs develop over time.

As you descend, the wreck becomes visible, resting on a sandy bottom. The upper deck starts at 12 metres, allowing for a gradual exploration of the superstructure. Below, the main deck lies around 24 metres, with the deepest parts of the wreck reaching 28 metres, a relatively shallow profile for a full wreck penetration. This depth range provides ample bottom time for divers to circumnavigate the vessel and observe its structural features.

Already, the HTMS Hanhak Sattru is proving to be a vibrant habitat. Large schools of snappers and fusiliers often aggregate around the deck and bridge, moving in unison as you approach. You'll regularly find groupers taking shelter within the superstructure, while trevallies, including both smooth-tailed and giant trevallies, patrol the perimeter of the wreck, hunting among the schooling fish.

Focus your attention on the exterior railings and decks, where nudibranchs and other small invertebrates are establishing themselves, adding intricate details to the developing ecosystem. Look into the shaded areas and crevices for moray eels, which have already begun to inhabit the wreck's many nooks. Batfish are also commonly spotted, often hovering in small groups around the more sheltered sections of the vessel.

This wreck offers a different experience compared to older, more heavily encrusted sites. Its relative newness means that the original structures of the fast attack craft are still clearly discernible, offering a unique opportunity to study the design of a military vessel in detail. The interaction between the clean lines of the ship and the nascent marine growth creates a dynamic and evolving underwater landscape.

Exploring the HTMS Hanhak Sattru provides insight into the early stages of artificial reef formation. While not yet as adorned with soft corals and sponges as older wrecks, the rapid colonization by fish and invertebrates demonstrates the resilience of marine life. This site perfectly complements the other wrecks in the area, like the HTMS Suphairin, HTMS Sattakut, and MV Trident, enriching Koh Tao’s reputation as an emerging wreck diving destination.