So, there were a lot of things I liked about this movie, and a lot of things I didn't.
As jrocxx (below) mentioned, the cat is kind of out of place with the scenery, and does resemble a rat in some scenes. I'm guessing that the cat is drawn relatively poorly in order for it to contrast from the scenery, but the problem is that instead of highlighting on the scenery or the story, it only takes away from the film. Simplicity is a good thing, but the cat is too simple and two-dimensional to fit in well with its high-quality, 3D surroundings, you know? For your next project, make sure that any contrasts add to the film, not take away from it. Also, one thing that bothered me for the first minute and a half of the film was the constant blurring and perspective changes. I know that was done to create an action scene where the boat is being rocked in the storm, and the island is sinking, but by overusing it, the effect went from intense to annoying very quickly. Because most of the screen wasn't in focus for so long, and the point-of-view kept changing/shaking, i quickly became confused, lost interest, and shortly afterwards became bored. There's nothing wrong with a good, long action scene, but don't overuse the same trick to the point where it makes viewing difficult and tiresome, else you may lose your audience.
However, that's not to say that this film wasn't great. I enjoyed the story, and thought that some of the backgrounds were amazing. Even though some of them were out of focus, (because the focus was on the cat), I personally thought that what i could see of them was amazing. The concept was unique, and it was clear that a lot of hard work was put into the film, especially in the motions of the fish.
I gave this film 2.5 stars because the film had a lot going for it, but was ultimately hindered by a number of things, mainly the constant lack of focus on the stunning backgrounds.