Honestly, Kayley, I can understand where you're coming from - it can be a bit confusing at parts, but over all I think it's a pretty easy concept to follow: woman wants to discover what happened to the man she loved while she was away, she gets washed away years later (personally I think the river was always meant to sort of be like Kate's memory, how it was all mixed up and unclear, but thanks to her being caught up in it again it helps to unlock what really happened that day for her) to see what really went on the three days she was gone. It is confusing in a few spots as I said, like my explaination I'm sure, but the basic overall story is that Kate loses the man she loves - she so badly wants to find out what happened that the "fates" as it were send her back - she gets to see what happened and she also gets to be with David more who in the end....
Highlight to read (for those who haven't seen it) -
she gets with. *Sorry if this doesn't work as well as I think it well, don't know the code for the spoiler effect.*
It's her getting to have her last good-bye to the past so she can move on to the future because without doing so she never would have and then she never would have gotten the ending she did in the movie. Lol, I'm starting to think it might be a little confusing to understand explain as well, or at least I'm doing a poor job on it so the best thing I can tell you is to watch it again - post the questions you have and then I can definitely help you from there. Or you could always ask *~Always_A_Star~* because it seems like she understands it as well, but might be a better translator for it.
Hope this helps if it can.
Great movie all the same, definitely recommend it for people who like the whole sci-fi feel to it, sci-fi feel being that it has the whole time travel thing going for it.