Bolinopsis rubripunctata near Chalok Bay

Boat dive

Chalok Bay

Chalok Bay is a sheltered, easygoing bay dive on the south side of Koh Tao, Thailand, reached by boat and running from about 3 m down to 12 m.

Depth
3-12 m
Level
Open Water
Visibility
18–29 m
Water
28–31 °C
Entry
Boat dive

Is it right for you?

Compare 2 dive centers
All 4 photos
The verdict

A good dive, worth a day.

Chalok Bay is a sheltered, easygoing bay dive on the south side of Koh Tao, Thailand, reached by boat and running from about 3 m down to 12 m. The bay hosts artificial reef structures, and divers report butterflyfish, angelfish, juvenile barracuda and stingrays.

Parrotfish, rabbitfish, giant barrel sponges and magnificent sea anemones have also been recorded in the area. The calm, shallow conditions suit Open Water divers, newer divers and anyone wanting an unhurried afternoon dive.

Location

Map & nearby sites.

Interactive map loads here. Every site on it is also listed on this page.

10.0618° N, 99.8259° EBoat dive · Koh Tao, ThailandOpen in Google Maps
Nearby sites straight-line distance, nearest first
Right now · updated 12 Nov 2026

November is a good month to dive.

November scores 7.2, 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+1.1° vs normalTick: normal for Nov, 28 °C
Visibility19 mtypical for NovPoor days 15 m · 1 day in 4 is worse
Waves1.2 mModerate6 s period
Reef stressNo stressNOAA Coral Reef Watch heat stress

Diving in Koh Tao in November

When to go

Best Jul-Oct.

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
JanFebMarAprMayJunJulAugSepOctNovDec
Water temperatureSurfaceDive depth28–31 °C
31°29°27°JFMAMJJASOND
VisibilityBad day to great dayTypical10–38 m
45255 mJFMAMJJASOND
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 %.
Marine life at Chalok Bay: percent chance per dive, by month
SpeciesJanFebMarAprMayJunJulAugSepOctNovDec
Ribbontailed Stingray3322369106333
Hongkong Butterflyfish172213101319263124221714
Yellow Scale Parrotfish1010881018252419191510
Moon wrasse886681117241511119
Thicklip wrasse9977101624221411108
Eightband Butterflyfish10976816232016171410
Tattooed Parrotfish997791623211515139
Doublebar Rabbitfish1110881217232219211812
Sling-jaw wrasse7755711162012788
Pastel-green wrasse77657121820131197
Lollyfish66446142096976
Wimple Fish11131010101216191514119
Marine life

What you'll see at Chalok Bay.

2.4Big draws. A shark, ray, turtle or other big draw on about 1 dive in 10 in the best months, most often ribbontailed stingray.
7.2Reef 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".

303 species likely at Chalok Bay: 84 recorded here, 219 at similar sites nearby, from divers' logs, GBIF and iNaturalist. iNaturalist observations by their observers, CC BY 4.0 and CC BY SA 4.0.See them by month
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
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Nobody has reviewed Chalok Bay yet. Be the first: reviews from divers with a logged dive here count most.

Dive centers

Two dive centers run Chalok Bay.

Confirmed: each lists this site on its own website. Listed alphabetically.

Dive centers whose own websites list Chalok Bay
DIVE CENTERAGENCIESNITROXCONTACTAction
Hydronauts Diving ResortKoh Tao
RAIDNot knownWebsite+ 66 080 065 8782OSMinfo@hydronautsdiving.comOSMView
New Heaven Dive SchoolKoh Tao
SSINot knownWebsite+66 77 457 045info@newheavendiveschool.comView

Not confirmedEight more centers likely dive here

These centers run trips to sites near Chalok Bay or are based within 10 km, but their own websites don't name Chalok Bay. Ask them before you book. Run trips here? Claim your listing and add it.

Dive centers that likely dive Chalok Bay, not confirmed
DIVE CENTER · WHY LISTEDAGENCIESNITROXCONTACTAction
Big Blue DivingNot confirmed Runs trips to Tao Tong, 1000 m away
SSINot knownWebsite+66 77 456 123View
Nava Scuba DivingNot confirmed Runs trips to Hin Ngam, 1.7 km away
PADIYesWebsite+66 77 601198OSMinfo@navascuba.comOSMView
Crystal DiveNot confirmed Runs trips to Aow Leuk, 1.9 km away
SSIYesWebsiteView
The Dearly Dive Koh TaoNot confirmed Runs trips to Aow Leuk, 1.9 km away
PADI, RAID, SSINot knownWebsite+66-(0)77-332-494info@thedearlykohtaohostel.comView
Dive Center "Scuba Birds"Not confirmed Runs trips to Shark Island, 2.1 km away
PADINot knownWebsite+66990307571info@scubabirds.comOSMView
Dive Poin Koh TaoNot confirmed Runs trips to Shark Island, 2.1 km away
SSIYesWebsite+66 77456231OSMView
French Kiss Divers - ChalokNot confirmed Runs trips to Shark Island, 2.1 km away
SSIYesWebsite+66641276082frenchkissdivers@gmail.comView
Goodtime AdventuresNot confirmed Runs trips to Shark Island, 2.1 km away
SSIYesWebsite+66872753604OSMView

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, geoparse, 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 Chalok Bay?

July, August, September, October score highest for Chalok Bay.

What certification do you need for Chalok Bay?

Open Water. Open Water Diver (or equivalent), typically to 18 m. Depth 3-12 m.

Destination · Koh TaoDiving in Koh Tao.Best Mar-May5 days of diving23 graded sitesThailandOpen the Koh Tao guide
How we grade

One number, built from dives people actually logged.

Never paid for. Dive centers can reply, not change a score.
  • 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.
  • 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. Here: the 2024 marine heatwave (peak 7.8 °C-weeks of heat stress), −0.8.
  • 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, geoparse, 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 47 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

Bolinopsis rubripunctata near Chalok Bay: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY). Copperband Butterflyfish near Chalok Bay: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY). Blackblotched Porcupinefish near Chalok Bay: (c) portioid, some rights reserved (CC BY), via iNaturalist (CC BY). Houndfish near Chalok Bay: (c) Иван Ковтун Ivan Kovtun, some rights reserved (CC BY), via iNaturalist (CC BY).