note represent this first paragraph be spoiler free . swim pool be about the author sarah morton play by charlotte rampling and and her run in with the daughter of her publisher name julie play by ludivine sagnier and while sarah stay be her publisher house to get settle into to write a new book . rampling be terrific a a secluded author who find both disgust and intrigue into julie . sagnier be decent a the publisher wild daughter who be promiscuous and be defensive against a scolding sarah . eventually they come together and even find thing they have in common and on the way toward sarah help julie out after something terrible happens . sarah main motive in all of this seem to be to write a book and but there authentic interest and especially in her stare on julie which neither seem scold nor approve . i like the dynamic between the two character and even a a certain major event seem quite unlikely . spoiler spoiler spoiler bellow the movie end with an extraordinary twist and i think i understand it . i will say this twist do not make me like the movie more and and may of even make me like it less and but whatever one think about it it certainly be different . you can not compare the twist to the sixth sense or fight club and or the crying game and and so on and because those twist make you simply look at event in a different light while they do not change what have actually occur ( though i guess fight club do change event to an extent ) . my theory be this . the real daughter julia actually stay with her and but the movie be represent her imagination of a more attractive and delinquent daughter name julie . at the end sarah say to her publisher that there be thing he keep from her and and that be one of the reason she decide to go to another publisher while something she find out be hidden from her and and the real daughter could be that . the cross replacement thing would make sense with a julia a she would far more likely be religious than someone like julie . the theory of julie be a real illegitimate daughter of another mother have one flaw and almost fatal and and that she do not look surprised at the end when she see julia and her father . that make it seem that either she never meet one of his daughter and or do in fact meet that one . and just an imagination julie and nothing else do not explain what she meant by her publisher hide thing from her . also the very end with the wave sequence of both julia and julie show the first a it really happen and and the second a she imagine it . i can not say this theory be certain and and maybe there no one certain answer and but i think it hold water more than the others .