I'm for the Hippopotamus (1979)

In 1950, in Africa. Tom organizes safaris for tourists, secretly equipping them with guns loaded with blanks. When Slim, Tom’s cousin—a sly slacker and staunch environmentalist—arrives, the two men come into conflict with Jack Ormond, a local animal trafficker. A doctor, a friend of the duo, denounces Mr. Ormond’s exploitation of animals in a newspaper, prompting Ormond to send his henchmen to destroy the clinic where the good doctor practices. But at the medical facility, Ormond’s henchmen find Tom and Slim waiting for them, and in the blink of an eye, the two cousins wipe out these thugs in a brawl. Ormond then tries to bribe the two cousins, and when that fails, has them imprisoned for a theft they never committed. After escaping from prison, the two men rush toward Ormond’s ship, beating the merchant’s men to a pulp...