Jerome's fall from the boat chapters 11-19?

Jerome attempted to edge him out far enough on a branch that he could wash himself, but it was too cold, and he changed his mind. When he turned back, the branch gave way, and he fell into the river.

It was bitterly cold. The wind cut like a knife. I thought I would not throw the water over myself after all. I would go back into the boat and dress; and I turned to do so; and, as I turned, the silly branch gave way, and I and the towel went in together with a tremendous splash, and I was out mid-stream with a gallon of Thames water inside me before I knew what had happened.