WELL,you can defined this great film just by one particular scene: the old man is rich,have good social position and took the boy on board to play the role of his mentor.However the young man was dragging the beautiful knife,which was_as he claimed_ the most important thing in his life.The guy was always playing the knife between his fingers and the old man was jealous about that.So when the boy went inside the yacht leaving the knife,the old man took the knife and tried to do the same.Suddenly the young appear and saw this.The only way for the old man to get away with some honour was to allow the boy do the play:he played the knife between the old man's fingers,looking straight into his eyes.Well the lady at the same time was swimming using a funny rubber cocodrile.So, imagine this beautiful scene with the knife,all the tension and suddenly we hear the woman shouting:'Andrzej, Andrzej,the cocodrile is making the bubbles',huh,when I was in the cinema the whole audience burst laughting after hearing that!. The woman stays in the background, just think why? There's another great funny shot when the woman lays there for a sunbathe with her small bikinis,well, her breast dominates the scene!. is the waving movement of the yacht who creates the sensual scene!.
Of course this scene was part of the longer plot ,the critics described this `knife scene' as the most famous and symbolic scene in all of Polanski films..Zygmunt Malanowicz,the actor who played the part of the young man said that he practice a lotnfor those scenes,polanski was afraid if he was prcticing long enough,finally everything was Ok.As Leon Niemczyc,the actor who played the mature role said" Malanowicz only gave me sligh scars'.The idea of the film was the strange competition between this two men.the jury and the prize was the woman.Polanski said he needed a actress that looked plain and normal in ordinary dress but intriguing in bikini!.
Polanski was not only interested in this kind of personages,he likes the relantionship between' the master and the servant' The domineering and the repressed ,as we can see in his short film' The Fat and the Lean' (1961, B&W, 15mins) or in features like Knife in the Water (1962); Cul-de-sac (1966);Dance of the Vampires(1967) etc.