In the scene where Tom Hanks is on his raft at night and a whale comes up for air right next to him, the whale disappears below the waves without so much as a ripple: A CG whale simply pasted onto a real water scene (the footage is much more compelling than my description) Obviously it would be impossible to use a real whale, but this made it painfully obvious that it was computer generated. They didn't use ILM, that's for sure!

Cheers,

Erik