I'm looking for the name of a movie, anyone want to help?

I saw this movie sometime in the late 90's on either nickelodian or some kids channel. It involes a kid who wants to go on an adventure and his grandma gives him a blank magical book, so that onc he opens it, he falls into the pages, and the first scene after doing that involves a mermaid savig him from drowning, andthen she grows legs and journeys with him and some other people. Another scene is where the boy is stuck in a tree of pizza's and he puts gum on the pepperoni and feeds it to the sand gator so that it can get stuck, but other than that, I can't really remember too much or can't find it anywhere, anyone want to help?