A red and yellow flag indicates the area patrolled by lifeguards
A red flag indicates conditions are too dangerous for bathing (but not necessarily for other sports)
A black and white quartered flag indicates the area for surfing and other sports
Find out about the beach and tide times before you enter the sea
I have included plenty of local information about the beaches on this site. Alternatively, ask the lifeguards.
Swim within your ability
If you're not a strong swimmer or not used to sea swimming, go to a lifeguarded beach. The red and yellow flags indicate the area patrolled by lifeguards, and this is the safest place to swim. A red flag means conditions are too dangerous for swimming, whilst a black and white quartered flag marks an area for non-powered water craft. Note that lifeguards have to train regularly - this is done before or after their shift. Their usual duty times are from 10 am to 6 pm. If you're on the beach outside these times, lifeguards may be training. Although they will obviously repond to any incident they are aware of, they will not be actively scanning the sea area and the red / yellow flags will not be displayed.
Swim where and when it's safe
Lifeguarded beaches are the safest places to swim, and the high tide period is generally the safest time. Deeply indented bays are usually safe, as are long straight sandy shores away from river estuaries, although there may be a cross current on these. Steeply sloping sand usually indicates fast currents, and undulations in the sand are often the result of rips.
Take care with inflatables
Check the wind speed and direction before using inflatables in the sea. Never use them if the wind is strong or blowing offshore.
Don't sit under cliffs
Always keep a safe distance in case of rock falls
Supervise young children
Don't let them enter the water or wander off by themselves, especially on busy beaches. Much of a lifeguard's time is spent searching for lost children.
Take care not to get cut off by the tide
Places you're likely to get cut off include:
Bays or long stretches of coast backed by high cliffs
If you venture into such places be sure you know the tide times and which way the tide is going. Large sandbars are usually a maze of banks and water channels, with these channels quickly filling and widening on the incoming tide.
Rip currents at Monkstone
Beware of currents
A rip current is defined as water flowing out to sea. These can be recognised by an area of calmer water in breaking waves, and discoloration caused by sand being picked up off the bottom. They are rarely very wide, and if caught in one you should swim across it, not against it. Rips and other strong currents can occur :
Near points, headlands and harbour walls
Between islands and the mainland
On beaches in the vicinity of a strong tidal flow
Near river estuaries
In surf conditions, particularly on steeply shelving beaches
Jumping / diving from rocks
Always check the water below regularly for depth, obstructions and currents. The Bristol Channel has the second highest tidal range in the world, and at mid tide, the water depth can drop by a foot in 10 minutes.
Don't dig deep or tunnel into sand
Sand is unstable and very heavy. Tunnels will collapse without warning.
Adder at Ynyslas, Ceredigion
Look out for adders on dunes and coast paths
Adders are often to be found basking in the sun on dunes and coastal paths. They are Britain's only poisonous snake and can be recognized by a zig-zag stripe along their back. This camouflages them well against a stony background. Away from the beach, wear proper shoes and never put your hand into rock crevices. In the very unlikely event of being bitten, you should call an ambulance and make your way to the nearest road as quickly as possible. The only other snake you're likely to see is the (harmless) grass snake, which has distinctive yellow markings on its head.