Swimming water quality

The official swimming season for recreational water is from 1 May to October. Especially in summer, hot weather can have a negative effect on water quality.

During this period the water quality of more than 100 areas in South Holland is tested every two weeks. The province only checks the 20 official swimming areas listed on the website of the Province of Zuid-Holland.

Three types of signs can be posted at individual sites:

• warnings (waarschuwing): swimming is permitted, except for young children, pregnant women and the elderly
• negative swimming advisory (negatief zwemadvies): swimming is not prohibited, but it is not recommended because of the increased health risk
• swimming prohibited (zwemverbod).

Health risks

Since natural ponds and lakes are not continually replenished and filtered like swimming pools, swimming outdoors in a natural environment can involve certain health risks.

The health risks include headaches, stomach problems, diarrhoea, fever, vomiting, itching, eczema, eye and ear irritation. These are usually caused by the absorption of toxins released by algae or the ingestion of flatworm larvae. 

Botulism is generally harmless to humans. Always make sure that your pets do not drink contaminated water! You can swim without the risk of bacteria in the North Sea.

Swimming Hotline

The Province of Zuid-Holland has also set up a special Swimming Hotline (Zwemwatertelefoon) providing the latest information on swimming water quality. Simply call (070) 441 75 50. The helpline is open from 8.30 until 16.00 hrs.

You can also send an e-mail to zwemwater@pzh.nl or consult teletext page 725 (in Dutch).

Safety tips

In all cases, you should take the following precautions:

• Swim only in areas where the swimming water is monitored.
• Do not overexert yourself.
• Avoid swimming for two hours after a heavy meal or after drinking alcohol.
• Enter the water gradually, especially after prolonged exposure to the sun, in order to prevent hypothermia.
• Never leave children unsupervised.
• Never swim on your own.
• Do not dive into unfamiliar, murky or shallow water.
• Do not swim near jetties, sewage outlets, dams or strong currents.
• It is forbidden to swim near bridges, landing stages, locks and marinas.
• Always stay close to the bank.
• Wear swimming shoes in order to prevent injuries from glass, metal objects or sharp stones.
• Do not swim in algae (especially blue and red algae).
• Do not swim close to large groups of aquatic birds.
• Do not swim close to rats.
• Do not swim if you see the bodies of animals or other detritus floating on the water surface.
• Do not throw left over food or packaging into the water; this encourages the growth of harmful bacteria.
• Try to avoid swallowing too much water while swimming.
• Leave the water if you feel ill or are injured.
• Never swim if you have open wounds on your skin.
• In the event of storms, move away from the water and find shelter (not underneath a tree, but in a car, for example).
• Always wash your hands after swimming and before eating.
• Take a shower after swimming and put on dry clothes.

Of course, if the conditions are unsuitable for outdoor swimming, you can always visit one of the swimming pools in The Hague.