Tonton Streaming Back to the Future (1991) S1E12 - Gone Fishin'

When Doc was four, he fell into a river during a fishing trip and has had a fear of it happening again ever since. After the boys learn about this, they and Marty try to change it. But they regret it when it leads to a mishap with a stunt plane, causing young Emmett Brown to become a famous daredevil.