Paul Revere was watching the water.

Between 9 and 10 p.m. on the night of April 18, 1775, Joseph Warren told Revere and William Dawes that the king's troops were about to embark in boats from Boston bound for Cambridge and the road to Lexington and Concord. Warren's intelligence suggested that the most likely objectives of the regulars' movements later that night would be the capture of Adams and Hancock. They did not worry about the possibility of regulars marching to Concord, since the supplies at Concord were safe, but they did think their leaders in Lexington were unaware of the potential danger that night. Revere and Dawes were sent out to warn them and to alert colonial militias in nearby towns.[40][41]