Short answer
A red flag on a Phuket beach means do not enter the water at all. Lifeguards raise red flags where rip currents are likely, mostly on the west-coast beaches during the south-west monsoon, and double red flags mean the sea is strictly off limits. In June 2025 three tourists drowned within two days at Karon, Kata and Bang Tao, all despite red flags. Swim only between the red-and-yellow flags where lifeguards are on duty, and if a rip catches you, swim parallel to the beach.
A red flag means do not enter the water
The rule is simple and the authorities repeat it. In June 2025 the Phuket Tourist Police urged visitors to obey the red no-swimming flags and to enter the water only where it is safe and where lifeguards are on duty. They said red flags signal hazardous conditions such as strong currents and rough seas, where swimming is strictly prohibited, and that swimming is allowed only in clearly marked zones that lifeguards can watch.
The flags work in pairs. The International Surf Lifesaving Association told The Phuket News in July 2018 that visitors should swim only between the red-and-yellow Swim Here flags, and only at beaches where lifeguards are visible. In May 2026 Thailand's Department of Disaster Prevention and Mitigation added that double red flags indicate extremely dangerous swimming conditions, and that entering the sea is strictly prohibited.
Why the west coast is dangerous in the wet season
Phuket's west-coast beaches face the Andaman Sea, and in the south-west monsoon the swell comes straight in. The UK Foreign Office says the rainy season generally runs from May to October and that people have drowned in strong riptides. On 19 May 2026 The Phuket News reported a Thai Meteorological Department warning of waves of two to three metres in the upper Andaman Sea, higher in storm areas, with red flags raised at several beaches including Patong.
In July 2018 the surf lifesaving association named the west-coast beaches it considered exposed: Nai Harn, Kata Noi, Kata, Karon, Surin, Bang Tao, Layan, Nai Yang and Mai Khao. It warned of fixed and flash rip currents, high surf and dangerous shorebreaks, and said conditions change rapidly. That list is eight years old, but the geography has not changed: the beaches that face west take the swell.
June 2025: three drownings in two days
The risk is not theoretical. The Phuket News reported on 13 June 2025 that three tourists had drowned at Phuket beaches in two days: one at Karon Beach on 10 June, one at Kata Beach and a third at Bang Tao Beach on 11 June. The Phuket Tourist Police said all three drownings occurred despite red no-swimming flags being posted. One of the victims had arrived on the island earlier the same day and went swimming shortly after checking in.
The same report said Patong lifeguards had rescued seven people from the surf in a single day that week, two of whom needed hospital treatment, and that rough seas and strong rip currents pose serious risks even to experienced swimmers. Strong swimming does not protect you from a rip; it only changes what you do wrong when one catches you.
What a rip current is, and what to do if one catches you
A rip current is a narrow band of water flowing out through a gap in the waves, often at a break in a sandbar. Wikipedia's rip current article explains that a rip does not pull a swimmer under the water: it carries swimmers away from the shore. Swimmers who are unaware of this can exhaust themselves trying to swim straight back against the flow.
The advice is to swim at a right angle to the flow, parallel to the beach, to leave the current. If you cannot, relax, float or tread water, and let the current carry you until it dissipates beyond the surf line, then signal for help or swim back diagonally, away from the rip. The National Weather Service advises talking to the lifeguard before you go in, so you know where the lifeguards are.
Calm weather does not mean a safe beach
Rip currents can form on days that look perfect. The US National Weather Service says rip currents often form on calm, sunny days, and that great weather for the beach does not always mean it is safe to swim or even play in the shallows. Its advice is to check conditions before going in, to talk to the lifeguard, and to swim only at a beach with lifeguards.
In Phuket that means looking at the flags first, every time. Flags change during the day as the sea changes: in July 2018 the surf lifesaving association said it would re-evaluate swimming areas at 6 pm. The UK Foreign Office adds that Thailand has lifeguards on duty at designated beaches and a flag system, and that jellyfish can come close to shore in the rainy season from May to October.
Late October is still the wet season
The calendar helps less than the sea. On 26 October 2026 Thailand's Department of National Parks reported heavy, continuous rain that caused flash floods and mudslides in Phuket, especially around Patong. That is a land report, not a swim warning, but it shows the weather is still unsettled. The UK Foreign Office gives May to October as the usual rainy season but notes that weather patterns have become increasingly unpredictable, so the flags decide each day.
Treat the beach flags as the first test and the lifeguards as the second. The World Health Organization's May 2026 drowning fact sheet says the risk of drowning increases when children are in water without active adult supervision, and links higher rates among men to swimming alone and to drinking alcohol before swimming alone. The Thai authorities and the UK Foreign Office both tell visitors to follow warning signs, and especially red flags.
What this means for a boat day in the monsoon
Boat days follow the same sea. On our Phi Phi and Maya Bay speedboat tour from Phuket, from $75 per person, the swim stops are Pileh Lagoon and Bamboo Island, with a mask, snorkel and life jacket included. If the sea is unsafe, the operator moves the trip to another date or refunds it. Maya Bay itself is closed every year from 1 August to 30 September.
A Phuket to Phi Phi ferry company says in its terms that it may cancel or change a service without notice because of poor weather, and The Phuket News reported that small boats were advised to stay ashore in May 2026. If you want the calm months, November to April is the season, and the August and September guide explains what the tour sees during the closure.
Practical checklist
- Look at the flags before you walk to the water, and swim only between the red-and-yellow flags.
- Do not enter the water when a red flag is up, and never when double red flags fly.
- Swim only at beaches where lifeguards are on duty.
- If a rip catches you, swim parallel to the beach or float, and signal for help.
- Keep children under active adult supervision in the water, as the World Health Organization advises.
- Ask your hotel about jellyfish and sea conditions between May and October.
Questions and answers
What does a red flag mean on a Phuket beach?
Do not enter the water. The Phuket Tourist Police say red flags signal hazardous conditions such as strong currents and rough seas, where swimming is strictly prohibited. Swim only in marked zones where lifeguards are on duty.
What do double red flags mean?
In May 2026 the Department of Disaster Prevention and Mitigation said double red flags indicate extremely dangerous swimming conditions, and that entering the sea is strictly prohibited.
Which Phuket beaches have the most rip currents?
The west-coast beaches that face the monsoon swell. In July 2018 the surf lifesaving association listed Nai Harn, Kata Noi, Kata, Karon, Surin, Bang Tao, Layan, Nai Yang and Mai Khao as exposed. Check the flags on the day.
What should I do if I am caught in a rip current?
Do not swim against it. Swim parallel to the beach to leave the current, or float and let it carry you beyond the surf line, then signal for help or swim back diagonally, away from the rip.
When is the dangerous season in Phuket?
The UK Foreign Office says the rainy season generally runs from May to October. The Phuket Tourist Police linked the June 2025 drownings to the south-west monsoon, but flags still decide each day.
Are there lifeguards on Phuket beaches?
Yes, at designated beaches. The UK Foreign Office says Thailand has lifeguards on duty at designated beaches and a flag system. Enter the water only where lifeguards are on duty.