Prince William has recorded a video message outlining importance of teaching children to swim.
It follows a report by the Amateur Swimming Association (ASA) which shows more than half of children aged 7-11 years cannot swim 25 metres unaided.
"Swimming has always been important to me," the Duke of Cambridge said. "Swimming is unique, it is the only sport that can save lives, which is why I'm so keen for school swimming to be accessible for all children at all primary schools."
He added: "The ability to swim changes lives, it brings huge joy and it can keep us fit and healthy. But above all, it can keep us safe, which is why I'm pleased to lend my support to this campaign."