Its plot follows a husband and wife who are accompanied on a boating trip by a young male hitchhiker, who spurs a number of escalating confrontations between the couple.

[8] Andrzej (Leon Niemczyk) and Krystyna (Jolanta Umecka) are driving to a lake to go sailing when they come upon a young man (Zygmunt Malanowicz) hitchhiking in the middle of the road.

The title refers to the major turning point in the film when Andrzej taunts the young man with the latter's treasured pocket knife, which is accidentally lost overboard.

"[9] The screenplay for the film, written by Polanski, Jakub Goldberg, and Jerzy Skolimowski, was initially rejected by the Polish Ministry of Culture due to its "lack of social commitment.

[10] After making a number of minor edits to the screenplay—mainly snippets of dialogue demonstrating "social commitment" to "appease the Ministry [of Culture]"—Polanski again pitched the project to the national film board, who approved it for production.

While the sailboat was large enough for the three actors, it was quite cramped for the film crew, who often had to hang over the side of the boat with safety harnesses in order to shoot.

[13] Knife in the Water was nominated for Best Foreign Language Film at the 1963 Academy Awards,[14] the first Polish motion picture to receive this kind of recognition.

[23] Knife in the Water was the basis for a low budget 2001 American film Kaaterskill Falls, set in the Catskill Mountains.