Factual error: Young David focuses his telescope at the moon. A close up shot then shows a circular view i.e. it is supposed to be the view through the telescope. Both the moon and the clouds in focus. With a telescope the depth of field is short and, with the moon in focus, the clouds would actually be blurred.
Cocoon (1985)
1 factual error - chronological order
Directed by: Ron Howard
Starring: Brian Dennehy, Steve Guttenberg, Hume Cronyn, Wilford Brimley, Don Ameche
Deliberate mistake: David spots the boat with the old folk on and runs around the harbor, down the jetty and jumps towards the dive boat as it leaves the jetty. He doesn't jump very high and you can see he would miss the rail on the boat. In the next shot, a (larger) stunt double is shown leaping high in the air onto the boat and, of course, catches the rail.
Art Selwyn: Men should be explorers, no matter how old they are. I don't know about anybody else, but I'm going.
Trivia: Some of the cloud effects were created by dumping colored dyes in tanks of water which were then superimposed into the shot.