When I was visiting a Dublin pub in about 1968 the musicians would bob up and down randomly and not together for Dingle Regatta. It was quietly explained to me that this was to confuse the Yankee tourists who were keen to join in but could not figure out when they should bound up.
Later I used the idea for a kids song, calling it Dingwall Regatta. When I was a Dingwall kid we would see yachts racing down down the Cromarty Firth, the race started by the firing of a gun. See my creation at https://www.youtube.com/watch?v=BBm6c7LL3aM.