Eaux profondes is a 1981 French thriller film directed by Michel Deville that stars Isabelle Huppert and Jean-Louis Trintignant.

[1] Based on the novel Deep Water by Patricia Highsmith, it tells the story of a man who regains his wife's affections by killing two of her lovers.

When soon after she brings home yet another lover, this time Vic researches the man, finding that he is a private investigator hired by Mélanie to keep an eye on him.

After she tells Vic one morning that she is leaving with Cameron, driving into town he sees the man and asks him into the car to discuss things.

Investigating the unexplained disappearance of a man who had not paid his hotel bill, the police question Vic as the last person to see him and then close the file for lack of evidence.