Upon jumping over the puddle...
On jumping over the puddle...
Is the jump completed or underway? And do the prepositions on and upon have the same meaning in that respect?
Upon jumping over the puddle she misjudged how wide it was and stepped into the water.
On jumping over the puddle she misjudged how wide it was and stepped into the water.
Are both sentences idiomatic? Only one of them? Neither of them?