What do the warning flags on a beach mean?

Beach flags are the sea's version of traffic lights, with one complication: not every country agrees on the colours. A flag that means "swim here" in Cornwall can mean something rather different in Sardinia or Florida. The good news is that every lifeguarded beach explains its own system, usually on a board at the entrance, and the lifeguards are there to answer questions. This is a summary of official guidance in our own words; follow the local signs, rules and lifeguards wherever you swim.

The UK system

The Met Office's beach safety advice, which draws on the RNLI, sets out the flags used on lifeguarded UK beaches:

• Red and yellow (a pair): the lifeguarded area, the place to swim, bodyboard and use inflatables.
• Black and white chequered (a pair): the zone for surfboards, paddleboards, kayaks and other non-powered craft, and where kitesurfers and windsurfers launch and land. Do not swim or bodyboard there.
• Red: danger. Do not go in the water under any circumstances.
• Orange windsock: offshore or strong wind. Do not use inflatables, which can be blown out to sea.

The same advice says that if you are unsure what a flag means, ask a lifeguard. Paired red-and-yellow flags are also the familiar signal in Australia; the International Life Saving Federation's beach safety page talks about swimming between the red and yellow flags on patrolled beaches.

The Italian system

Beach safety in Italy is regulated by local ordinances, so the details have varied from place to place over the years, and older signs may still show other combinations. Some recent ordinances use a green, yellow and red system; the 2025 beach safety ordinance of the Comune di Maracalagonis in Sardinia, for example, sets out:

• Green: lifeguard service active, favourable conditions.
• Yellow: lifeguard service active, but sea and weather conditions potentially risky.
• Red: swimming discouraged or dangerous, with or without lifeguards, and also flown when the lifeguard service is not running, together with a sign warning that swimming is not safe.

Ordinances are set locally, so check the board at your stabilimento or the public beach entrance. You may also see a red flag with a white diagonal stripe on a float out on the water. That is not a swimming warning: the same ordinance requires anyone swimming or diving beyond the bathing area to tow a float carrying that flag, so boats can see them.

The US system

On many US beaches, flags follow definitions from the United States Lifesaving Association, which the Alabama Department of Public Health summarises. Yellow means a medium hazard with moderate surf or currents, red means strong surf or currents and everyone is discouraged from swimming, double red means the water is closed, purple means marine pests such as jellyfish or stingrays, and red-and-yellow means a lifeguarded zone.

What to do on any beach

• Read the board. It will explain the flags, the lifeguard hours and any local rules.
• Swim where and when lifeguards are on duty, inside the marked zone.
• Treat a red flag as a no. Even strong swimmers get caught out by waves and currents.
• Ask. Lifeguards would far rather answer a question than perform a rescue.
• Learn about rip currents, which can be hard to spot. Our page on rip currents covers what official bodies advise.
• In an emergency, call for help. Alert the lifeguards; in the UK, the Met Office advice is to dial 999 or 112 and ask for the Coastguard, and 112 is free everywhere in the EU, Italy included.