Oh, right. Toxic River is a level way down the track. Bloody impossible.
I did find Sunshine head to get into at first, because aiming the water jet was pretty tricky, and squirting away all the gunk gets a bit tedious after a while. Once you get the hang of the controls, though, it gets better. Plus, as the game moves on, it becomes less about cleaning stuff up, and more classic 3D Mario, requiring precise jumps, quick reflexes and stuff.