Peaks in AugDoublebar RabbitfishSiganus virgatusSeen here
13%of dives
Photo: H. Schlegel, via Wikimedia Commons · PD · taken elsewhere
Boat dive · Drift · Wreck
HTMS Hanhak Sattru Wreck
This former Thai Navy vessel, the HTMS Hanhak Sattru (also known as 312), was sunk in September 2023 in Aow Mao Bay on Koh Tao's quiet east coast, making it one of the island's newest wrecks.
Also called 312, Ao Mao, Aow Mao Bay, Aow Mao Hanhak Sattru, HTMS Hanhak Sattru, Hanhak Sattru
- Depth
- 16-28 m
- Level
- Open Water
- Visibility
- 18–30 m
- Water
- 28–31 °C
- Entry
- Boat dive
The verdict
A good dive, worth a day.
This former Thai Navy vessel, the HTMS Hanhak Sattru (also known as 312), was sunk in September 2023 in Aow Mao Bay on Koh Tao's quiet east coast, making it one of the island's newest wrecks. It sits upright on the seabed, with the dive ranging from about 16 m down to 28 m and pairing the hull with relaxed reef scenery.
Barracuda, trevally, queenfish, titan triggerfish and groupers are among the fish reported around it. The site is reached by boat and is open to open water divers, though it can be dived as a drift.
Location
Map & nearby sites.
Interactive map loads here. Every site on it is also listed on this page.
Right now · updated 12 Nov 2026
November is one of the best months here.
November scores 7.3, against 7.4 in its best months. Live sea readings from NOAA Coral Reef Watch and NOAA WaveWatch III as of 10 Nov 2026.
Water30 °C+1.2° vs normalTick: normal for Nov, 28 °C
Visibility21 mtypical for NovPoor days 17 m · 1 day in 4 is worse
Waves1.2 mModerate6 s period
Reef stressNo stressNOAA Coral Reef Watch heat stress
When to go
Best May-Nov.
Every month gets its own Divegrade score from that month's marine life, visibility, reef and reviews. Across Koh Tao as a whole, the best months are Mar-May.
Divegrade score by monthPick a month for its full guide
Water temperatureSurfaceDive depth28–31 °C
VisibilityBad day to great dayTypical10–39 m
How is this measured?
Mostly from years of satellite readings of how clear the water is around this site. Each bar runs from a bad day, which about 1 day in 10 is worse than, to a great day, which about 1 day in 10 beats; the line marks a typical day. Satellites can't see through cloud, so stormy days are underrepresented and the real bad days can be murkier. For 12 months here, local dive centers report worse days than the satellites see, so the bar starts at their figure. Logged dives will sharpen it over time.
Chance of seeing it on a dive, by monthThe big draws first, then the most frequent. Share of sampled dive days that recorded the species. Months with few dives on record lean on the months around them and the rest of the year, and are shown lighter. A dash means under 1 %.
| Species | Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Doublebar Rabbitfish | 10 | 11 | 10 | 9 | 8 | 11 | 20 | 22 | 16 | 16 | 13 | 10 |
 Pearly Monocle Bream | 8 | 9 | 8 | 8 | 10 | 11 | 16 | 17 | 14 | 10 | 9 | 8 |
 Neon Damselfish | 8 | 8 | 7 | 8 | 9 | 10 | 12 | 11 | 9 | 16 | 13 | 8 |
 Tattooed Parrotfish | 8 | 9 | 9 | 9 | 10 | 11 | 16 | 15 | 10 | 13 | 12 | 8 |
 Indo-Pacific Giant Barrel Sponge | 7 | 7 | 7 | 5 | 5 | 8 | 14 | 15 | 13 | 7 | 7 | 7 |
 Moon wrasse | 8 | 8 | 8 | 8 | 9 | 11 | 15 | 14 | 9 | 12 | 11 | 8 |
 Scissortail sergeant | 8 | 9 | 8 | 8 | 9 | 10 | 14 | 15 | 10 | 13 | 12 | 9 |
 Golden rabbitfish | 6 | 6 | 6 | 7 | 8 | 9 | 9 | 5 | 6 | 15 | 11 | 7 |
 Hongkong Butterflyfish | 9 | 9 | 10 | 13 | 12 | 12 | 14 | 10 | 11 | 14 | 12 | 9 |
 Bridled beauty | 7 | 8 | 7 | 7 | 9 | 10 | 12 | 10 | 11 | 14 | 10 | 8 |
 Wimple Fish | 6 | 6 | 6 | 5 | 4 | 7 | 13 | 10 | 6 | 8 | 7 | 6 |
 Mourning Dorid | 7 | 10 | 12 | 8 | 4 | 4 | 4 | 2 | 2 | 4 | 7 | 6 |
Marine life
What you'll see at HTMS Hanhak Sattru Wreck.
0.5Big draws. None recorded often enough here yet to count.
6.6Reef life. Variety: how many different species a few dives here turn up, compared with other sites.
The big draws first (sharks, rays, turtles, octopus and the like) when they turn up on at least 1 dive in 20 in their best month, then the regulars, ranked by how often divers record them across the year. Each percentage is the share of sampled dive days that recorded the species. Where this site has few records of its own, sightings from similar nearby sites (same side of the island, similar depth and exposure) are added at a lower weight and marked "seen nearby".
Peaks in Aug
Best Apr–NovHongkong ButterflyfishChaetodon wiebeliSeen nearby
11%of dives
Peaks in AugPearly Monocle BreamScolopsis margaritiferaSeen here
11%of dives
Photo: (c) Bernard DUPONT, some rights reserved (CC BY-SA) · CC BY SA · taken elsewhere
Peaks in JulTattooed ParrotfishScarus rivulatusSeen here
11%of dives
Best Jul–NovScissortail sergeantAbudefduf sexfasciatusSeen here
10%of dives
Photo: Unknown author, via Wikimedia Commons · PD · taken elsewhere
Best Jul–NovMoon wrasseThalassoma lunareSeen here
10%of dives
Photo: Leonard Low from Australia, via Wikimedia Commons · CC BY 2.0 · taken elsewhere
Photos
4 photos. All from this site.
Divers pick the cover photo. Open any photo and vote for it; the one with the most votes leads this page.
Diver reviews
No reviews yet.
Verified dives count more.
Reviews linked to a logged dive, and reviews from experienced divers, carry more weight in the score.
- 2.5×
- a review backed by a logged dive here, vs. one that isn't
- 2×
- a review from a 100-dive diver, vs. a first-timer's
Dived HTMS Hanhak Sattru Wreck?Sign up free to share how it went. Import your dive log and your review counts as verified.Share how it went. Divers with a logged dive here get the verified badge.
Nobody has reviewed HTMS Hanhak Sattru Wreck yet. Be the first: reviews from divers with a logged dive here count most.
Dive centers
Two dive centers run HTMS Hanhak Sattru Wreck.
Confirmed: each lists this site on its own website. Listed alphabetically.
| DIVE CENTER | AGENCIES | NITROX | CONTACT | Action |
|---|---|---|---|---|
Big Blue DivingKoh Tao | SSI | Not known | Website+66 77 456 123 | View |
Hydronauts Diving ResortKoh Tao | RAID | Not known | Website+ 66 080 065 8782OSMinfo@hydronautsdiving.comOSM | View |
Not confirmedEight more centers likely dive here
These centers run trips to sites near HTMS Hanhak Sattru Wreck or are based within 10 km, but their own websites don't name HTMS Hanhak Sattru Wreck. Ask them before you book. Run trips here? Claim your listing and add it.
| DIVE CENTER · WHY LISTED | AGENCIES | NITROX | CONTACT | Action |
|---|---|---|---|---|
Crystal DiveNot confirmed Runs trips to Laem Thien Bay, 550 m away | SSI | Yes | Website | View |
Goodtime AdventuresNot confirmed Runs trips to Aow Tanote, 1.2 km away | SSI | Yes | Website+66872753604OSM | View |
Nava Scuba DivingNot confirmed Runs trips to Aow Leuk, 2.8 km away | PADI | Yes | Website+66 77 601198OSMinfo@navascuba.comOSM | View |
New Heaven Dive SchoolNot confirmed Runs trips to Aow Leuk, 2.8 km away | SSI | Not known | Website+66 77 457 045info@newheavendiveschool.com | View |
The Dearly Dive Koh TaoNot confirmed Runs trips to Aow Leuk, 2.8 km away | PADI, RAID, SSI | Not known | Website+66-(0)77-332-494info@thedearlykohtaohostel.com | View |
Dive Center "Scuba Birds"Not confirmed Runs trips to Shark Island, 3.6 km away | PADI | Not known | Website+66990307571info@scubabirds.comOSM | View |
Dive Poin Koh TaoNot confirmed Runs trips to Shark Island, 3.6 km away | SSI | Yes | Website+66 77456231OSM | View |
French Kiss Divers - ChalokNot confirmed Runs trips to Shark Island, 3.6 km away | SSI | Yes | Website+66641276082frenchkissdivers@gmail.com | View |
OSM From OpenStreetMap (© OpenStreetMap contributors, ODbL), not from the center's own website.
Safety & rules
Know before you drop.
Depth, current and certification are safety calls. This isn't a dive briefing: your guide gives that on the boat or at the entry.
Hazards
No specific hazards recorded. That doesn't mean there are none: ask locally.
Rules and requirements
- Who can dive it
- Open Water Diver (or equivalent), typically to 18 m. Koh Tao sites for Open Water divers
- Local rules
- No specific rules recorded.
- Park fee
- None known
- Sources
- Dive center websites, derived, geonames, NOAA Coral Reef Watch and NOAA WaveWatch III.
If a diver is hurt: oxygen first, then call for helpFor suspected decompression sickness give 100% oxygen right away and contact local emergency services. DAN emergency hotline: +1 919 684 9111. Check where the nearest recompression chamber is before you travel, and carry dive insurance with evacuation cover.
Questions
When is the best time to dive HTMS Hanhak Sattru Wreck?
May, June, July, August, September, October, November score highest for HTMS Hanhak Sattru Wreck.
What certification do you need for HTMS Hanhak Sattru Wreck?
Open Water. Open Water Diver (or equivalent), typically to 18 m. Depth 16-28 m.
How we grade
One number, built from dives people actually logged.
- Big draws or varietyMarine life scores the better of two things: how often sharks, rays, turtles and other big draws turn up, and how varied the reef life is, plus a little for having both. Both are per dive, so busy sites can't win on volume.
- By monthEvery month has its own score. Pick a month to see yours.
- Thin data, cautious scoreFew dives or reviews? The score leans toward the regional average.
- Graded as a wreckThe wreck itself counts for 35% of the score and marine life 20%. Heat stress on coral does not apply to the wreck's own grade.
- Reef healthThe reef score counts coral variety, and recent marine heatwaves that bleach coral take up to 3 points off it, fading over the years after as the reef recovers.
- Hard isn't worseCurrent and depth are shown on their own. A tough site can still score 10.
Sources for this page
Site facts: Dive center websites, derived, geonames, NOAA Coral Reef Watch and NOAA WaveWatch III. Occurrence data from GBIF.org; sea conditions from NOAA Coral Reef Watch and Copernicus Marine. Score computed 12 Nov 2026 from 38 logged dives and 0 reviews: medium confidence.
Water temperature: average surface temperature by month from NOAA OISST climatology; at a typical dive depth here from the E.U. Copernicus Marine Service ocean reanalysis. Visibility: NASA satellite water-clarity data, local dive center reports and logged dives.
Photo credits
Bubble Coral near HTMS Hanhak Sattru Wreck: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY). Jewel Damsel near HTMS Hanhak Sattru Wreck: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY). Hong Kong Butterflyfish near HTMS Hanhak Sattru Wreck: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY). Surf Parrotfish near HTMS Hanhak Sattru Wreck: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY).