The young girl is airborne as she falls into the lake.
A girl is falling off a pier, into a lake.
A pier isn't the only object that the girl can launch off of to fall into the lake. Falling into the lake doesn't imply she fell off something in the first place.
Just because a girl is airborne it does not mean she is falling off a pier.
Girl is airborne as she falls does not imply that she is falling off a pier.