Armand Mestral and Edmund Purdom in WHITE SLAVE SHIP
This is an extremely rare film, in English anyway. Mestral starred in MORGAN THE PIRATE. Purdom was a PEPLUM star and eventually lived in Rome until his death. A great looking film which takes place entirely on the boat. I recently got hold of two copies, in French and Italian, but I haven't watched either of them in full, just scanned parts of it, and it looks good.