A Royal Thai Navy fast attack craft sunk at the mouth of Laem Thian bay, around 60 m north of the headland, and now a wreck dive that sits entirely within recreational depth. She is 44.9 m long and 7 m wide, lies in about 23 m of water with her mast reaching up to roughly 13 m, and is the same class of ship as the HTMS Suphairin 313 in No Name Bay.
Also known as HTMS Hanhak Sattru 312 Wreck.
Where it is and how deep
10.0927° N, 99.8543° EPublished position for this site.
The dive
The wreck lies about 60 m north of Laem Thian, on the mouth of the bay, in roughly 23 m of water. Her mast comes up to around 13 m, which gives the dive a useful shape: the top of the rigging is the first thing you meet on the descent and the last thing you leave, so groups can drop onto a known depth, work down the length of the ship and then use the mast as the reference for the ascent rather than crossing open sand to find a line.
She is a compact ship, 44.9 m long and only 7 m across the beam, so a single circuit at deck level covers most of her and there is time to go back over the parts worth a second look. She was sunk recently rather than long enough ago to be heavily colonised, so the hull, the deck and the mast still read clearly as a warship. The 23 m seabed keeps no-stop time reasonable, but it is still deep enough to plan the profile before entry.
The wreck
- Vessel
- HTMS Hanhak Sattru 312
- Type
- High-speed attack ship, Royal Thai Navy
- Length
- 44.9 m (147 ft)
- Cause
- Not published; the source records only a recently sunk vessel at the mouth of Laem Thian bay
- Lies
- About 60 m north of Laem Thian in roughly 23 m of water, mast reaching to about 13 m
HTMS Hanhak Sattru 312 belonged to the Gulf Patrol Fleet of the Royal Thai Navy and was built by Singapore Ship Building and Engineering Co., Ltd. She is a high-speed attack ship, 44.9 m long and 7 m wide, and she is the same class as the HTMS Suphairin 313, which lies in No Name Bay off Koh Nang Yuan on the other side of the island. Between them the two ships give Koh Tao a matched pair of navy wrecks on opposite coasts.
Marine life and season
The sources we used don't single out particular species here.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| Good | Good | Prime | Prime | Prime | Good | Good | Good | Good | Fair | Fair | Good |
Season follows Koh Tao: No official closure; whale shark sightings peak March-May and September-October, while October-November bring more rain and surface chop.
Know before you go
- The seabed is at 23 m and the wreck is intact enough to tempt divers inside: any part of the hull is an overhead environment, so stay outside it without wreck training, a torch and a guide.
Questions divers ask
How deep is the HTMS Hanhak Sattru 312?+
She sits in approximately 23 m of water at the mouth of Laem Thian bay, with the mast of the ship reaching up to around 13 m, so the whole wreck falls inside recreational depth.
Is this the same wreck as the HTMS Sattakut?+
No. The Hanhak Sattru 312 is a separate ship, sunk around 60 m north of Laem Thian on the east coast. She is the same class as the HTMS Suphairin 313, which lies in No Name Bay.
Sources
- HTMS Hanhak Sattru 312, Wreck - Scubago — Scubago
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