This movie makes my head spin trying to figure everything out.

The way i took it, according to what Juile told Sarah,I thought she actually was John's illegitimate daughter by a mistress, only she was posing as his daughter "Julia" in order to protect John's secret. Julie told Sarah that her mom wanted John to leave his family for them but he wouldn't do it. So i thought that if Julie really is john's daughter, John felt some responsibility to her, therefore he gave her a key to his house in France and probably, being the rich publisher he was, provided money to her. At the end, Julie tells Sarah that the scar on her abdomen was a result of a car accident. The fact that this was brought out tells me Julie's mother probably died in the accident, only Julie was just injured. There's really no other reason to bring this fact out in the movie. Again, i have to wonder that if Julie was John's daughter by a mistress, why would he send Sarah there, KNOWING that Julie would probably show up? Wouldn't he want to keep Julie's existence a secret?...When Sarah first got to the house, she called John and asked him when he would come up. John said something like, "well it depends on how work goes."...I took this to mean he was deliberately avoiding coming to the house because his illegitimate daughter would be there...and i found it odd that after Julie shows up at the house, Sarah was not able to contact him ever again during the entire movie, until the end. One time Julie was on the phone, supposedly talking to John. Julie asks John, "did you ring mom up? Well you need to call her. She is still waiting." Then she hands the phone to Sarah, but when Sarah tries to talk to him, he HUNG UP.....i guess my whole point is, John obviously had a family in England. I would think if he had a child by a mistress, he would want to keep it a secret. So again, that being the case, why would he send Sarah there, knowing Julie would probably show up?...I feel almost certain that Sarah's final book, "The Swimming Pool", was Julie's mom's unpublished book that John had read years ago and told her to burn because it was no good, mainly, because of the fact that Julie said in her note, "maybe you can use her book as a way of bringing her back to life," therefore, why didn't John recognize Sarah's final book at the end? ...a lot of the posters here seem to think Julie didn't really exist and that it was all a fictional part of Sarah's book but i don't know....i hate movies like this...i prefer movies that are completely LINEAR and easy to keep up with and follow...i don't like to have to rack my brain trying to figure out deep, artsy-fartsy movies like this....because if i don't understand them, i don't get nearly as much enjoyment out of them....

I just had another thought: After Julie kills Franck, Sarah asks her why she did it. Julie replies, "I dont know...i guess for the book you are writing"...so yeah maybe this is a good indicator that all this was happening in Sarah's mind for the book she was writing and maybe none of it was real. Also, at the very end, they show Sarah standing on the balcony at John's house and waving to Julie who is standing at the edge of the swimming pool, only this time its the REAL Julie instead of the first Julie that spent all that time with her at the house. I think after Sarah sees the real Julia in John's office, maybe she could now put a real face to the Julie she made up while at John's house, and in a mental fantasy, that's what she was doing. But did Sarah know that John's Daughter was named "JULIA?"...If she knew this, the movie never indicated as such... I wish i knew for sure all the answers to this movie. It will bug me forever probably, until i do....

OK....Three hours later after my above theories, I have re-watched the movie and think i have it figured out. At the beginning of the movie she is in John's office. She is PISSED at him...she says "you never look after me anymore" and stuff like "you didn't even like my last book yet you didn't have the balls to tell me"....then she says "i'm fed up with murders and investigations" and John says "then why don't you confound your critics and write something completely different?"....He then suggests she go up and stay in his house in France...she asks "will you come visit me?"...he says, "well i have my daughter but maybe i can come on the weekend"....she uses this conversation as inspiration for her next book....she writes it out of spite for John, who she is disgusted with....she makes up this huge imaginary story of an illegitimate daughter of john's named "JULIE"....the only thing is, at the end, we see his real daughter and her name is "JULIA"...sort of a strange coincidence that his real daughter's name is only one letter different from the "JULIE" she made up...not sure how this happened....so that raises more questions....but i am now in agreement with the other posters that all that happens in the movie after she arrives at the villa in France is all made up out of Sarah's head...when she gets to the house in France, i don't think she immediately starts out writing about Julie...but then she goes out on the balcony and sees the swimming pool....that starts giving her ideas about the Julie story and THAT is what starts her novel.....and from time to time, she goes out to the balcony and looks at the pool, then the next scene is usually her typing again....so between the pool and her contempt for John (including the fact that John can afford to buy a mansion like this because of HER books), she is "inspired" for the Julie story....thus the title of the movie, "SWIMMING POOL"....TA DAHHHHH!!!!...i hope i never see another movie like this as long as i live....LOL!