The Watch Water is a river in the Scottish Borders area of Scotland. It rises in the Lammermuir Hills, around 8 kilometres (5.0 mi) west of Longformacus, and flows generally eastward to its confluence with the Dye Water, around 700 metres (2,300 ft) west of Longformacus. The Dye Water flows into the Whiteadder Water, which in turn is a tributary of the River Tweed.