1. He overbalanced and fell head first.

2. The ladder overbalanced on top of her.

3. He overbalanced and fell into the water.

4. Halfway along the wall he overbalanced and fell.

5. She fell with a sharp cry of surprise, and the ladder overbalanced on top of her.

6. She wasn't quick enough to let go and it overbalanced her and she plunged into the water next to him.