HTMS Sattakut (LCI-739 Wreck)

Overview: Koh Tao’s Premier Wreck Dive

The HTMS Sattakut (LCI-742) is a 49-metre (160-foot) decommissioned US Navy Landing Craft Infantry ship that served in the Pacific theatre during WWII (including the Battle of Iwo Jima) before being transferred to the Royal Thai Navy.

On 18 June 2011, she was intentionally scuttled by the Thai Department of Marine and Coastal Resources just 50 metres off Sairee Beach to create an artificial reef and wreck training site. The wreck sits upright in a natural sand channel at a maximum depth of 30 metres, with the wheelhouse rising to 18 metres and the bow 76mm cannon at 22 metres.

Detailed Dive Route

• Descent: Down the bow or stern buoy line directly to the wheelhouse at 18m.
• Bow 76mm Cannon (22m): Swimming forward along the main deck to the iconic forward gun mount, a favourite photography location.
• The Hull & Portholes (26m–28m): Swimming along the port and starboard sides, inspecting the open troop quarters and engine room access hatches.
• The Stern & Anti-Aircraft Guns (24m–30m): Exploring the rear twin 40mm Bofors anti-aircraft gun mounts and the massive rudder resting in the sand at 30m.
• Reef Transition: At 110 bar, ascend to the wheelhouse roof (18m) and take a 3-minute swim east across the sand to finish your dive on the shallow coral gardens of Hin Pee Wee (6m–12m) for your 5m safety stop.

Training & Safety Rules

• Certification Required: Advanced Open Water (30m) or Wreck Specialty.
• Penetration Rule: Do not enter the internal cargo holds or engine room without certified wreck penetration training, guidelines, and redundant gas/lighting. Silt build-up inside the hull can reduce visibility to zero in seconds if kicked with fins.

Technical Dive Profile & Navigation

1. Entry & Descent Mechanics

• Descent Method: Direct giant-stride or negative back-roll from the boat, descending along the shot line to prevent surface drift.
• Ear Equalization: Equalize continuously every 1 metre during the descent phase to prevent sinus or middle-ear barotrauma.
• Compass Heading & Navigation: Set a primary heading toward the main reef structure. Maintain buddy contact within 2 metres throughout the descent.

2. Deep Section & Gas Management (14m to 30m)

• NDL Discipline: At depths of 30m, your No-Decompression Limit ticks down rapidly. Monitor your dive computer continuously.
• The Craig Rule: Divers certified to Open Water level (18m maximum) must stay on the upper reef shelf and never follow advanced divers down past 18m.
• Turnaround Gas: Signal your buddy and start your ascent when the first diver reaches 110 bar (or one-third of usable cylinder capacity).

3. Ascent & 5m Safety Stop

• Ascent Rate: Ascend along the reef wall at a controlled rate not exceeding 9 metres per minute.
• Mandatory Safety Stop: Complete a strict 3-to-5-minute safety stop at 5 metres (15 feet) before deploying an SMB and surfacing with a 360-degree overhead scan.

Marine Life & Habitat Zones (Biologically Verified)

• Apex & Pelagic Predators: Whale Sharks (Rhincodon typus), Chevron Barracuda (Sphyraena qenie), Queenfish (Scomberoides commersonnianus).
• Reef Fish & Keystone Species: Titan Triggerfish (Balistoides viridescens), Pink Anemonefish (Amphiprion perideraion), Giant Grouper (Epinephelus lanceolatus).
• Macro Biodiversity & Benthic Invertebrates: Janss Pipefish (Doryrhamphus janssi), Nudibranchs (Phyllidia varicosa), Banded Boxer Shrimp.
• Elasmobranchs & Marine Reptiles: Whitetip Reef Sharks, Leopard Sharks (Stegostoma tigrinum), Green Sea Turtles, Blue-Spotted Fantail Rays (Taeniura lymma).