Whale Shark Season — Sail Rock & the Gulf of Thailand
June whale shark likelihood: Moderate
Live satellite plankton (Koh Tao zone): 0.23 mg/m³ chlorophyll-a
June whale shark sighting likelihood at the Gulf pinnacles (Sail Rock, Chumphon, Southwest) is moderate — about 39% based on season and current plankton levels. Whale sharks gather at the Gulf's offshore pinnacles to feed on plankton — so we forecast the season from the same Copernicus satellite chlorophyll our dive-conditions tracker already reads. Peak is March–May, with a second pulse in September–October.
Whale shark odds, month by month
Climatological sighting likelihood at the Gulf pinnacles (Sail Rock, Chumphon, Southwest). Driven by the plankton-bloom cycle — the current month is highlighted with today's live signal.
How we forecast it — and the honest catch
Whale sharks are filter feeders. They don't follow the phytoplankton our satellites see directly — they follow the zooplankton that graze on it, which arrive a few weeks after a bloom. So when the Gulf's chlorophyll climbs (we read it daily from Copernicus Marine satellite data), the zooplankton — and the whale sharks — tend to follow.
That's why sightings cluster around the March–May bloom and a second September–October pulse. We treat this as a seasonal likelihood nudged by the current plankton signal — not a day-ahead guarantee. Marine life never reads the forecast.
The catch: the same bloom that brings the whale sharks also drops visibility. The best encounters are often on the shoulder of a bloom — enough plankton to draw the animals, clear enough water to enjoy them. Watch the live Sail Rock conditions and aim for a calm, clearing day.
Whale shark season FAQ
When is whale shark season at Sail Rock and Koh Tao?
Whale sharks are most reliable at the Gulf of Thailand pinnacles from March to May, with a second pulse in September–October. Both line up with plankton blooms. June whale shark sighting likelihood at the Gulf pinnacles (Sail Rock, Chumphon, Southwest) is moderate — about 39% based on season and current plankton levels.
Where are the best whale shark dive sites in the Gulf of Thailand?
The three offshore granite pinnacles between Koh Tao and Koh Phangan: Sail Rock, Chumphon Pinnacle and Southwest Pinnacle. Their plankton-rich upwelling draws filter feeders, including whale sharks and large schools of barracuda.
Does a plankton bloom help or hurt whale shark dives?
Both. Whale sharks follow zooplankton, which follows the phytoplankton bloom our satellite chlorophyll tracks — so a bloom raises your odds. But the same bloom lowers visibility, so the best encounters are often on the shoulder of a bloom rather than its peak.
Can you freedive with whale sharks at Sail Rock?
Yes. Sail Rock is one of the few places you can freedive alongside whale sharks on a calm day. Book an early-morning trip for flatter seas and fewer scuba bubbles, and check the live conditions score before you go.
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