Duffy (1968)

Half-brothers Stefane and Antony despise their biological father, callous millionaire Charles Calvert. Because Charles refuses to share his wealth with his sons, Stefane and Antony ask hip American thrill-seeker Duffy to help steal the money they believe is their birthright. When Charles decides to move a large portion of his savings from Morocco to France, Duffy has an opportunity to stage a daring burglary attempt at sea.