Now Bence had not calculated on this; he thought that if he got under the body or lowest level of the bore visible, he would find himself in still water.
Cheyne had also resolved on diving, but for a very different object.
Suppose he remained on the surface, the force of no mortal man could resist that wild rush of water, and the upward thrust which would strike him in the place where such a blow would be most effective--the chest. It would turn him over as a wind would a leaf. It would in all likelihood lift part of his body out of the water, and hurl him backward into the open beyond. The rush of the water must be borne, there was no way of avoiding that; but the uplifting might be avoided.
It was plain that when a torrent, or when in repose, the cleft held just the same quantity of water, from the dead-level line down. Not a gallon more water was below the low-level water-line when the bore dashed through the cleft than a second before the incoming of the wave.
Therefore the bore, as it were, ran along the low-level water; and although the water beneath would be pushed violently forward, the horizontal motion would not be quite as much as above, and there would be little upheaval.
But Cheyne knew what Bence did not know--that no man could, by swimming alone, stem the force of even that under-current.
"When I dive," he said to himself, "and get down there, I shall let go a pretty powerful grapnel. I shall moor myself on all-fours with my hands and feet."
He swam up the cleft, paying out his little coil of rope as he went, until he heard the roller break upon the outer rocks. Then, without waiting another moment, he dived.
When he found the descending force of the dive spent, he thrust out both arms and legs until they reached the sides, then working his legs up and his hands down, until he could get the full measure of his enormous strength to bear laterally upon the rocks, he thrust forward his head and awaited the onset.
When it came it was not quite as bad as he had anticipated; but the strain was tremendous. He had no difficulty in resisting it; but another man, a man of ordinary strength, would have been taxed to the utmost, and in all likelihood driven from his hold.