These imaginative figurines are made of stone and usually have a pipe ending with a spout in their mouth to spit water to the ground. The architects designed them to prevent the walls from being eroded by the rainwater running down the walls and thus minimizing the influence of the rainstorms. The length of the gargoyle determines, how far the water is spit from the wall.
In ancient times figurines
of strong animals i.e. lions were used for this job. In medieval ages the idea changed. Instead of real animals they used iconic daemonized figurines at the outer side of the facades to use them for avoiding the devil to come into and to shelter the building.
You can find them not only in the Normandie. Also Notre Dame de Paris has many of them. And you can find them also at many other old european churches, especially at churches build following the gothic style or the romanesque style and at churches build during Renaissance.