Police say the girl was learning to slalom ski on Newfound Lake in Hebron.
She fell and her father drove the boat back toward her.
Police say he briefly became distracted when his hat blew off his head.
He put the boat in neutral as it passed over the girl in the water at slow speed, but she suffered serious injuries to her torso.
She was rushed to shore, CPR was started, but she couldn’t be revived.
The girl’s mother and 14-year-old sister were also in the boat at the time.
Authorities say drugs and alcohol did not play a role in the incident and no charges are expected.