Southwest Pinnacle
Depth is the range from the top of the site to its usual maximum; "recommended cert" is the mainstream-agency level operators usually ask for, not a legal rule. Currents and visibility change daily — treat everything here as planning ranges.
Southwest is a drowned mountain range in miniature, a cluster of granite spires whose main summit reaches to about 6 m, all of it dressed in the same magnificent-anemone carpet that makes Koh Tao's deep pinnacles glow. It fishes like a smaller, calmer Chumphon: grouper of genuinely surprising size holding in the gullies between spires, schools of snapper and fusiliers turning the towers into silhouettes, barracuda strung across the current line. Longfin batfish drift up to inspect masks. On quiet mornings it may be the most relaxing of the island's big three, and whale sharks include it on their rounds.
The moment you come for: Spire-and-gully topography, outsized groupers, anemone glow with fewer boats
Topography: Cluster of granite spires rising from about 30 m
Know before you splash
Hazards: Mid-gulf position brings current and chop; watch depth in the gullies.
Conservation: Fishing lines snag the deeper spires; crews remove what they can, divers report the rest.
Nitrox: Worth it here — profiles sit in the range where enriched air meaningfully extends no-stop time (with the training to use it).
Who you'll meet
Clownfish & Anemonefish
Giant Grouper
Great Barracuda
Pinnate Batfish
Whale Shark
For photographers
Wide angle: ★★★★☆ · Macro: ★★☆☆☆ — editors' 1–5 rating of what this site gives each style of shooting