Milford Haven Waterway (Welsh: Dyfrffordd Aberdaugleddau) is a natural harbour in Pembrokeshire, West Wales. The Haven is a ria or drowned valley flooded at the end of the last Ice Age formed by the Pembroke River and the Daugleddau estuary, and 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 Sri Lanka (then Ceylon) and "the finest port in Christendom".