People can again swim at hundreds of approved natural water sites that are deemed clean and safe from today. However, from the very beginning of the season, dozens of locations will already have warnings in place due to blue-green algae, poor water quality, or other special conditions.

Across the Netherlands, there are roughly 950 official swimming spots, including lakes, pools, and beaches. Water authorities regularly test these sites for things like bacteria and overall water conditions. Information on all locations, including current quality, facilities, and any warnings, is available on zwemwater.nl.

Swimming is banned straight away at two natural water sites: De Fontein in Gelderland and Vakantiepark De Betteld. In eight provinces, swimmers are being urged to be careful. Around 20 locations will have advisories against swimming on Friday morning due to poor water quality or contamination, and another 20 sites carry warnings, with possible health risks such as skin problems or stomach and intestinal issues.

People are responsible for avoiding these spots or being careful in the water and not swallowing it. Where a swimming ban is in place, police or enforcement officers can step in. Even at approved and safe swimming locations, authorities stress that swimming is always at your own risk.

According to BIJ12 on behalf of the provinces, bacteriological water quality has been up to standard at most swimming sites over the past two years, about 94 percent, ranging from excellent to acceptable.

Official swimming sites are checked throughout the season, with water quality and surroundings monitored up until October 1.

Warnings have also been issued regarding the temperatures of the water. It is estimated to be around 11 degrees Celsius. The Rescue Brigade Netherlands has warned people not to stay in the water for too long.