Why is it important to throw a stone from the cliff?

Behind the scene of a 33 mn documentary available here:
https://www.reelhouse.org/seb.montaz/...

The Flying Frenchies are back, with more fantastical stunts and enthralling experiments in a whirlwind adventure to the fjords of Norway. Twenty or more of the most colourful characters you could ever imagine, each with a different skill or talent, working together to create an outdoor extravaganza the likes of which have never been seen before!