Wife Swap.

A. While wife is home making sex with her lover, hubby comes home unexpectedly causing the lover to run and hide in the closet. Paul playing the husband, handles it with aplomb however and narrates a flashback that explains his situation, then allows Steve to fuck his wife while he watches. B. Couple walking on the beach discover a lone girl photographer, wife encourages her husband to pick her up and make love to her while she takes photos. C. Husband of couple A inserts part C into wife of couple B, daughter of couple A does husband of couple C. It gets more confusing but everyone involved has a really good time. D. Craig tells his wife he's going fishing then sneaks back to try and catch her with another guy but much to his happy surprise it turns out wifey's lover is another woman.