There is a lot wrong with this
First off I'm going to comment on the soundtrack. When the music picks up into that hard rock it doesn't end, which leads me to believe that you didn't make the layer that music track was on into a "stream" and have a "stop" key frame at the end of it. Also, why hard rock? Why not some crazy bongo drums to go with what's happening in a scene? That's a mistake many people make, by putting in music that they LIKE instead of what fits.
Another thing I'm going to comment on is the one still shot of the shark you kept on using. I would go back and animate his tail and his gills atleast go give him better movement. Using a still over and over again and just moving it around with tweens is incrediably boring and will lose interest to your audience.
But you did have some nice drawings, so you do have skill there. All I suggest is to keep at it and when you work on something submit it in a place where people can critique it, like the NG Mags section. That and keep practicing at your animating. I hope this critique helps.