Ao Mae Yai is the largest and calmest bay on the northern island of the Surin Islands (Mu Ko Surin National Park) in Phang Nga, Thailand, and is widely rated as one of the country's finest shallow-reef snorkeling spots. Its gently sloping 1-6 m depths make it comfortable for beginners floating at the surface, while a vast hard-coral garden of lettuce, plate and branching corals hosts large schools of tropical fish and, with luck, sea turtles. Visibility is typically 15-30 m and the water a warm 28-30 C. Note that a survey on 26 June 2026 recorded roughly 10% coral bleaching in the bay after sea temperatures climbed to 30-31 C, and the park is now monitoring the reef every 15 days.
The largest, calmest bay on North Surin Island — gentle shallows ideal for first-time snorkelers
An expansive hard-coral garden mixing lettuce, plate, branching and soft corals
Big schools of tropical fish including angelfish and parrotfish
Chance to see sea turtles (keep your distance)
The inner bay is a conservation zone — snorkel only in the permitted area near Cape Mae Yai
The Moken (sea gypsy) village on nearby Ko Surin Tai
Good to know
SafetyCurrents can strengthen at the bay mouth and around Cape Mae Yai and may push you toward open water. Never snorkel alone, carry a float or surface buoy, and stay inside the permitted zone.
SafetyAt low tide the water can be barely 1 m deep, so it is easy to scrape on coral or get stung by sea urchins or fire coral. Never stand on the bottom — stay horizontal and keep your fins up.
SafetySeveral tour boats anchor inside the bay, so watch boat lanes and stay visible. This is a remote island with limited medical facilities, so don't push yourself if your mask fogs or you feel panic.
SeasonThe national park opens only around 15 October to 15 May (08:30-16:30) and closes entirely during the monsoon (mid-May to mid-October). The best months are November to April.
SeasonWarming seas (30-31 C) caused about 10% coral bleaching in the bay in 2026 and conditions may shift, so check the latest reef and reopening status around the 15 October reopening.
RulesThis is a marine protected area and part of the bay is a no-entry conservation zone. Do not touch, stand on or break coral, don't collect shells or coral or feed the fish, and use reef-safe sunscreen. Confirm entrance-fee and licensed-tour requirements.
MannersIf you meet a sea turtle, keep your distance and never chase or touch it. When visiting the Moken village, wear a shirt and ask permission before taking photos.
Practical info
Access is by speedboat from Kuraburi Pier (about 85 km / 1.5 hours from Khao Lak) or Nam Khem Pier; there are no public ferries, only private tour operators. Park tents and bungalows are available, and day trips and overnight tours run from Khao Lak. Entrance fees, tour prices, operating hours and whether the park is open all vary by season, so confirm the latest details before booking.
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