He made his debut for the club on 13 October 1934, ten games into the 1934–35 season, and scored the winning goal in Blackpool's 2–1 victory over Norwich City at Bloomfield Road.

In 1936–37, Watmough scored thirteen goals in his 31 league appearances, helping the club to a runners-up finishing position and promotion to Division One.

In their first season back in the top flight, 1937–38, Watmough's place came under pressure from Alex Munro, who was signed from Hearts.

Watmough made fourteen league appearances and scored two goals before he was sold to arch-rivals Preston North End in early December 1937, in an exchange deal that brought Frank O'Donnell to Blackpool and also took Jim McIntosh to Deepdale.

Watmough's final game for Blackpool was in a single-goal defeat at home to Liverpool on 27 November.