Three men – two Polish nationals and one German – died while swimming in two separate accidents in the Dutch North Sea on Sunday.

One man died after getting into difficulties close to the Zuiderstrand near The Hague, the other two at the Wassenaarse Slag beach, the Dutch lifeboat association said.

The deaths come as the national statistics agency published new figures showing a sharp rise in deaths by drowning last year. In total 138 people died in drowning accidents at sea and on lakes and rivers in 2018, of whom 26 were visitors.

The lifeboat association said that the hot weather last summer is likely to have encouraged more people to take a dip. ‘Last year our beach patrols were called into action 7,900 times, 2,400 more times than in 2017,’ the association’s director Koen Breedveld told broadcaster NOS.

The increase is among adults, not children, and the number of under-20s dying in drowning accidents remains around 14 a year.

Between 2014 and 2018, 563 people died by drowning in Dutch waters, of whom around 147 lived in the Netherlands and had a migrant background, and 120 were foreign visitors. Of them, around one third were German nationals and 18% Polish, the CBS said.