The African Queen

The African Queen (1951) Directed by John Huston Starring: Humphrey Bogart Katharine Hepburn, Robert Morley, Peter Bull
In WWI East Africa, a gin-swilling Canadian riverboat captain is persuaded by a strait-laced English missionary to undertake a trip up a treacherous river and use his boat to attack a German gunship.
The African Queen (1951) on IMDb