They waited for another shot, but none came.
The reason was this: the herd of wild elephants which Bruce and the colonel had heard came charging almost directly toward them, smashing young trees and trampling the tough underbrush.

Some of them made for the water directly in line with the passing boats.

Kathlyn, keenly alive to the fact that here was a chance, jumped overboard before Umballa could reach out a staying hand.
To Kathlyn there was only death in the path of the elephants; to remain on the barge was to face eventually that which was worse than death.
Her arm throbbed painfully, but in the desperate energy with which she determined to take the chance she used it.

Quite contrary to her expectations, her leap was the best thing she could have done.

Most of the barges were upset and the great beasts were blundering across the river between her and the barges.
Bruce witnessed Kathlyn's brave attempt and dashed into the water after her.