It's not mandatory but as far as I know it's pretty much a given that you send your kids to swimming lessons. People that can't pay for swimming lessons for the

It's not mandatory but as far as I know it's pretty much a given that you send your kids to swimming lessons. People that can't pay for swimming lessons for their kids can request government help to pay. Generally when kids are about five years old they'll start with "Zwemdiploma A" ("swimming diploma A"), which you often need to even be allowed to enter the deeper pools. When you don't send your kids to swimming lessons you potentially deprive them of fun days away with their classmates because they need that swimming diploma to be allowed to come.