 The Daugleddau estuary winds west to the sea.As one of the deepest natural harbours in the world, it is a busy shipping channel, trafficked by ferries from Pembroke Dock to Ireland, oil tankers and pleasure craft.Admiral Horatio Nelson, visiting the harbour with the Hamiltons, described it as the next best natural harbour to Trincomalee in Ceylon (today's Sri Lanka ) and "the finest port in Christendom".