Warnings issued at more Dutch swimming locations as water quality worsens

Health risk warnings have been issued at more than 100 swimming sites in the Netherlands due to poor water quality, significantly more than earlier in the summer. 

Blue-green algae in many swimming locations in the Netherlands

An analysis by ANP of data from Zwemwater.nl, which provides live updates about the water quality of swimming locations throughout the Netherlands, showed that more than 100 of the 950 official swimming sites currently have health risk warnings, reports Hart van Nederland. In June this year, this number was significantly lower at just 46 sites.

The water at swimming locations, such as ponds, lakes and recreational waters, is often checked for health risks like blue-green algae or bacteria. Many of the swimming locations with health risk warnings are due to blue-green algae, which can cause skin irritation and digestive issues if swallowed. 

According to Hart van Nederland, water quality can deteriorate when warm weather persists for a long period of time, similar to what we have been experiencing in the last few weeks. 

Drowning risks increase with hot weather

During the heatwave in June, there were a number of swimming-related deaths, especially in inland waters. Based on research done in the UK, for every degree of average temperature rise, the risk of drowning increases by 7 percent.

In 2025, 100 people drowned in the Netherlands and research from Statistics Netherlands (CBS) found that there was a higher risk among children with a non-Dutch background. 36 percent of all drownings last year were among internationals.

There is specifically more risk in outdoor swimming locations, as most people have learned to swim in a swimming pool with clear water and a solid bottom, while conditions are very different at other swimming sites. "Pits, silt, stones, small plants, and animals. It can also be much shallower than expected, or there may be an invisible undertow," a scientist who has been researching drownings for 40 years, Joost Bierens told NOS. 

When a swimmer first encounters something unexpected like this, they can start to panic and get themselves into a dangerous situation. “The recovery time is extremely short. To get the situation under control, you have to manage to get your head above water again, and if you're not used to that, you're helpless," Bierens explains.

According to Bierens, more research is needed on how to prevent drownings in the Netherlands. "As a country rich in water, we in the Netherlands are lagging somewhat behind international developments.” 

Swimming safely in open waters

The Dutch Rescue Brigade (Reddingsbrigade) and Zwemwater.nl give some tips on how to swim safely in open water:

• Check the water quality of a swimming site before swimming
• Learn how to swim before entering open waters
• Never swim alone
• Only swim where it is allowed and where there is supervision
• Do not dive into unknown, shallow or murky waters
• Be careful swimming in cold waters, as they can cause muscle cramps and shock
• Leave the water during thunderstorms
• Wash yourself off after swimming in surface water and wash your hands before eating
• If you find yourself in trouble while swimming, it is important to stay calm, float on your back or grab onto something else that floats and call or wave for help