The video, shot by photographer Matt Porteous during the Waleses’ Easter break, showed the daredevil youngster launching himself into the water from a height, digging in the sand with a spade, playing cricket and running along the beach.
It was posted on the Kensington Palace Instagram account, accompanied by the message: “Thank you for all the birthday wishes for Prince Louis. 8 is great!”
The prince and princess earlier on Thursday released a new photo of Louis onboard a boat, also taken during their time away in the South West.
A grinning Louis was shown leaning with his arms folded against the vessel’s metal barrier, with the sea in the backdrop.
William and Kate’s youngest child, who is known for his cheeky nature, was wearing a blue textured quarter-zip style jumper.
The post on the Waleses’ social media read “Happy birthday, Louis! 8 today!” followed by a red balloon emoji.
The picture was also taken by Porteous, to whom the Waleses often turn to mark family occasions.
It is not known which beach the royals visited, but William inherited the vast Duchy of Cornwall landed estate and the title the Duke of Cornwall when he became heir to the throne in 2022.
Louis was last seen at church with the rest of the royal family on Easter Sunday.
A love of the water runs in the family.
William used to surf while studying in St Andrews, while Kate is a fan of cold water swimming.
Louis’s great-grandfather Prince Philip, the late Duke of Edinburgh, was known for his naval service, and became Admiral of the Fleet.
Louis’s grandfather the King also served in the Navy as the Prince of Wales, commanding HMS Bronington, and Louis’s namesake – Earl Mountbatten – became the First Sea Lord.