Rivers form when the water level drops at low tide. The water flows away between two higher sandbanks. This creates a deep channel that is perpendicular to the coast. The water in it has a high flow rate.
If you get into such a current, you can float tens of meters into the sea in no time. The current is too strong to swim with lifeguard certification against it. If you try to do that, you run the risk of getting tired and drowning.
It is better to swim with the current until it decreases. Swim diagonally and go back to the side over the sandbanks. You can recognize sandbanks by the foam on the waves. This foam is created when the waves break.
At the ripples it is deeper; the waves will not break there. Therefore, no foam mass will be formed.
If you see on the beach that someone needs help, do not jump into the dangerous sea current yourself, but contact lifeguards as soon as possible.
Offshore wind and upstream
When the wind blows from land into the sea (offshore wind), the top layer (upper current) of the seawater is blown off the beach into the sea. The stronger the wind, the stronger this upper current. It means you can easily float far out to sea (on a dinghy, pool, or inflatable crocodile) or swim. Swimming back to the beach is a lot more difficult, sometimes impossible if the current is strong. This is especially true for inexperienced swimmers and swimmers with poor fitness.
If you got too far out to sea, let yourself be carried away by the sea and see if you can discover a sandbank. And try to get the attention of the people on the beach. Swim as calmly as possible to conserve strength. Do not panic.
Onshore wind and undertow
Wind from the sea (onshore wind) pushes the water onto the beach. If that water flows back to the sea, a strong undertow can develop that pulls swimmers into the sea.
With strong onshore winds and strong surf, this undertow can be very dangerous. Children and the elderly are especially vulnerable, for example, if they are knocked over by a wave.
If such a dangerous situation arises, the rescue brigade raises a yellow or red flag. In that case, do not go – or no further than knee-deep – into the sea.
Angled wind from the sea
If the wind comes at an angle from the sea or blows along the coast, so-called zippers can arise. These are strong currents parallel to the coastline, which you can hardly swim against. These zippers are especially dangerous for small children.
If you end up in a zoo per, let yourself be carried away with the current and try to swim or walk diagonally to the beach.
Beach flags
Rescue teams have flags for the flagpole and flags for flagpoles at their post(s). These flags are hoisted or placed by lifeguards, according to the current situation. To inform bathers, swimmers, water sports enthusiasts, and other holidaymakers about and warn them about the risks associated with open water (sea and inland water).
Flags for flagpole
Red over yellow (rectangular flag)
Lifeguards present!
This flag indicates that the rescue station is open and the lifeguard work area is supervised by qualified lifeguards.
Red (rectangular flag)
No swimming! Very dangerous!
This flag indicates serious danger. This flag is raised when the conditions of the (swimming) water are very dangerous. Swimming, bathing, and other activities on or in the water are strongly discouraged.
Red over red (two rectangular flags above each other)
Swimming and bathing are prohibited!
These flags indicate a swimming ban. Swimming, bathing, and other activities on or in the water are prohibited. Ignoring this prohibition can be fined.
Yellow (rectangular flag)
Watch out when swimming! Dangerous!
This flag indicates danger. This flag is raised when the conditions of the (swimming) water are dangerous. Swimming, bathing, and other activities on or in the water are not recommended. Swimmers and bathers should be extra careful and vigilant.
Orange (windsock)
Watch out when swimming! Do not use propellants!
The windsock indicates that it is unsafe to go out on the water with (inflatable) flotation devices. The windsock is hoisted in offshore wind.
White with a blue question mark (rectangular flag)
Child found!
This flag indicates that a child has been found who is missing her/his parents and/or guardians. Parents/guardians are requested to report to the rescue post immediately.
Green with a white cross (rectangular flag)
First aid personnel present at rescue station!
This flag indicates the presence of first aid personnel at the rescue station.
Purple (rectangular flag)
Dangerous (sea) animals and/or vermin in the water!
This flag indicates that there are dangerous (sea) animals and/or vermin in the water. Swimming is not recommended.
Flags for flagpoles
Red over yellow (beach flags along waterline)
Swimming area supervised by lifeguards!
These beach flags indicate a defined swimming area. The area in between is under the permanent supervision of qualified lifeguards. Swimming between these flags is recommended. Water sports are not allowed in this area.
Black and white checkered (two rectangular flags along waterline)
Water sports area!
These flags indicate a demarcated water sports zone. An area or boundary of an area where water sports are practiced. Swimming in this area is strongly discouraged.
Red with ‘DANGER’ in yellow (two beach flags along waterline)
Area with dangerous conditions!
These beach flags indicate a demarcated zone where the conditions of the (swimming) water are dangerous. Swimming, bathing, and other activities on or in the water have an increased risk. Swimming between these flags is strongly discouraged.
Water quality
During the bathing season, the bathing water is regularly checked for contaminants that could make you sick.