Flash animation advice

Hello all! So i’m currently working on one animation that is going to become video in the future. But i have come across a difficulty. I have two views of a meadow. The first one is far and the second is close. My biggest problem is one lake which changes its shape during the closeup. I have the first and the last positions of the lake, but cant figure out how to transform from one to the other. So my request is for advice from your side. What is the best way to do this animation.