Barnacle Bill (released in the US as All at Sea) is a 1957 Ealing Studios comedy film, starring Alec Guinness. He plays an unsuccessful Royal Navy officer and six of his maritime ancestors. This was the final Ealing comedy (although some sources list Davy as the last Ealing comedy), and the last film Guinness made for Ealing Studios. His first Ealing success was in Kind Hearts and Coronets (1949), in which he also played multiple roles. The film was written by the screenwriter of Passport to Pimlico.

Plot

William Horatio Ambrose (Guinness) wants desperately to live up to the proud family tradition; the Ambroses have always been mariners (even if not distinguished ones), hence their family motto, "Omnes per Mare" ("All at Sea"). In humorous vignettes, Guinness portrays six of his ancestors, starting with a confused caveman perpetually going in circles in his coracle and ending with his own father's ignominious demise at the Battle of Jutland. Ambrose has a debilitating problem however: he suffers from violent seasickness. As a result, his contribution to the Second World War consists of testing cures for the malady.