Two youthful, unburdened women, Irem and Barbara, receive an invitation for a weekend boat trip aboard a yacht belonging to Giorgio, a man who is both heartless and disillusioned as a businessman. He’s married to Silvia, a woman struggling with emotional distress, who endures physical and psychological abuse from her husband. A romantic entanglement develops involving Silvia, Irem, and Barbara, leading them to plot against Giorgio, whose contempt for women and increasing suspicion ultimately result in his committing murder. The film feels like a blend of an Italian giallo, identifiable by its murder mystery and depiction of cynical upper-class Europeans, and an Italian “terror” movie such as "Late Night Trains," "Terror Express" (which also starred Dionisio), or "House by the Edge of the Park," also directed by Ruggiero Deodato. It isn't quite as brutal as a typical “terror” film, with more focus on the sexual freedom of the 1970s than on rape/revenge themes or other forms of violence. There are similarities to the later Australian movie "Dead Calm," and that might not be accidental since Charles Williams’ novel that inspired "Dead Calm" was written in the 1950s and circulated in Europe and America at the time as a potential project for Orson Welles. However, while “Dead Calm” explored sexual tension, this film prioritizes sex itself. The lovely Silvia Dionisio (whom Deodato later married—understandably so) is often seen without her clothes on, as is the actress playing the industrialist’s long-suffering wife. There's heterosexual sex, lesbian sex, three-way encounters, attempted assault, sexual degradation – just about everything. The underdeveloped murder storyline doesn't arrive until the film’s conclusion and seems rather routine. But it’s useful to have a sudden burst of violence to refresh your senses after experiencing what feels like an excess of explicit sexuality. This movie isn’t as disturbing or intense as Deodato’s later films, "Cannibal Holocaust" or “House by the Edge of the Park,” but it's likely more enjoyable to watch. It also signals the arrival of some promising talent in its female lead and particularly in its director.

Source on TMDB