then the waters of mithrim were overthrown and the incoming flood swept roaring up the channel and whelmed the rocky islets and churned the white sand -- so that tuor fled and was afraid , who did not know the ways of the sea ; but the ainur put it into his heart to climb from the gully when he did , or had he been whelmed in the incoming tide , and that was a fierce one by reason of a wind from the west .