Here's a 9:17 video
www.youtube.com/watch?v=_luN5weloqw that looks like maybe year-1965, or so? All the water skiers are wearing a skier's belt which is no longer legal in NH for water skiing.
Check out the one kid who skis with the tow rope handle held between his legs while he juggles two tennis balls at the same time.
Camp Idlewild was a summer camp for boys, ages 7-15, located on 200-acres of Cow Island, close to Tuftonboro and Wolfeboro, in operation from 1891 to 1970.