What happens that makes Crusoe think he will never make it back to shore?

Crusoe got stuck in a violent current and believed himself lost.

I found myself in a great depth of water, and a current like the sluice of a mill. It carried my boat along with it with such violence, that all I could do could not keep her so much as on the edge of it, but I found it hurried me farther and farther out from the eddy, which was on my left hand. There was no wind stirring to help me, and all I could do with my paddlers signified nothing. And now I began to give myself over for lost; for, as the current was on both sides the island, I knew in a few leagues distance they must join again, and then I was irrecoverably gone. Nor did I see any possibility of avoiding it; so that I had no prospect before me but of perishing; not by the sea, for that was calm enough, but of starving for hunger. I had indeed found a tortoise on the shore, as big almost as I could lift, and had tossed it into the boat; and I had a great jar of fresh water, that is to say, one of my earthen pots; but what was all this to being driven into the vast ocean, where, to be sure, there was no shore, no

mainland or island, for a thousand leagues at least."