The Magic School Bus at the Waterworks is the first book in the original book series.
Plot
While other kids go to the zoo or even the circus, Ms. Frizzle's class boards the bus to visit the waterworks. And to make matters worse, she herself is driving!
But it is soon apparent that this is no ordinary field trip. The bus suddenly leaves the ground! Ms. Frizzle parks it on a cloud, and everyone (even her) shrinks to raindrop size. Then the whole class begins to rain into a mountain stream below. They are seeing the waterworks from the water's point of view.