From Herodotus's day to the present political upheavals, the steady flow of the Nile has been Egypt's heartbeat. It has shaped its geography, controlled its economy and moulded its civilisation. The same stretch of water which conveyed Pharaonic battleships, Ptolemaic grain ships, Roman troop-carriers and Victorian steamers today carries modern-day tourists past bankside settlements in which rural life - fishing, farming, flooding - continues much as it has for millennia.