Ok, look at these pictures
A man may have been in a standing position & suddenly fell off with his head coming into contact with the floor first before other parts of his body (back, legs, etc).
fall (verb): 2 STOP STANDING/WALKING ETC [intransitive] to suddenly go down onto the ground after you have been standing, walking, or running, especially without intending to
I fell and hit my head.
slip/stumble/trip etc and fall
He slipped and fell on the ice.
Lizzie fell down and hurt her knee.
Peter was playing by the river when he fell in (=fell into the water).
fall to/on your knees (=move down to the ground so that your body is resting on your knees)
She fell to her knees beside his body.
dive: 1 JUMP INTO WATER to jump into deep water with your head and arms going in first dive into/off etc
She dived into a pool.
Diving off the cliffs is dangerous.
So do we say "She fell on her head", "She fell with her head onto the floor", "She fell and hit her head onto the floor" or "She dived into the floor" or "She fell & dived into the floor" (but for "dive" people do it on purpose not accidentally like "fall")?