Finding Nemo is about two fish, father and son (Marlin & Nemo). Nemo goes swimming out into the open, away from the reef where it's safe and gets taken by divers. The rest of the movie is about Marlin, his dad, looking for him. The whole time he is looking for him, there is always something that gets in his way. For example, an annoying fish follows him the whole way, they run into fish friendly sharks who end up trying to eat them and they get stung by jellyfish.
The graduate also has contains some obstacle that Ben has to overcome to get to Elaine in time. He sleeps with a married woman, he dates her daughter, Elaine, after the mom made him swear not to, he ends up falling in love with Elaine but she is about to get married to another guy. Ben decides that he has to stop her from marrying this other guy but on his way to the wedding he runs into a few obstacles, he has to stop for directions, his car runs out of gas so he has to run the last few blocks.
Pretty much, they both are about a guy (Ben & Marlin) going on a journey to get something they want (Elaine & Nemo). But on their way to getting what they want, they run into lots of things keeping from getting it.
One comparison I found between The Graduate and Finding Nemo is the editing of the scenes. They are all in order and most scenes contain major parts leading up the ending.
