A person just about to stand up while water-skiing, while people in the background watch and take photos.
The person water-skiing is about to hit a big wave.
Just because a person is about to stand up while water skiing does not mean that they are about to hit a big wave.
A person can water ski without being about to bit a big wave.
A person may stand up while water-skiing without any waves present so the person may not necessarily be about to hit a wave and waves may be sizes other than big.