Polanski writes:
Casting the journalist’s wife proved more difficult: I decided to look for a non-professional. On the strength of a screen test, I gave the part to Jolanta Umecka, whom I spotted while prospecting at a municipal swimming pool in Warsaw.
No comment necessary, perhaps. (A question: is this film the origin of Bishop from Aliens playing with the knife?)
Synopsis: On their way to an afternoon on the lake, husband and wife Andrzej and Krystyna nearly run over a young hitchhiker. Inviting the young man onto the boat with them, Andrzej begins to subtly torment him; the hitchhiker responds by making overtures toward Krystyna. When the hitchhiker is accidentally knocked overboard, the husband's panic results in unexpected consequences.