The Last of Sheila (1973)

Sheila is killed in a hit-and-run car accident following a party one night. A year later her multi-millionaire husband, Clinton, invites a group of her friends to spend a week on a his yacht. He's a notorious practical joker and insists his guests play a mystery game where each has been assigned a crime for the others to discover. Each night a series of clues is planted in the local port and the team must solve the identity of the criminal-of-the-day. However, things get out of hand and soon there's a real crime to solve.