Here are a few pics I dug up of le mascaret:
This first one, with le Mont-Saint Michel in the background, was taken at le Gué de l'Épine in le Val Saint-Père, just a few hundred metres down the estuary road from the highway you will be traveling.

The tidal bore ranges in height from a few feet to several metres, depending on the position of the sun and moon, weather conditions, and surrounding topography. Legend has it that it arrives at the speed of a galloping horse, but the one we saw seemed to be doing just an easy trot.
Below we see le mascaret as viewed from the bridge over the Sélune River in Pontaubault, (just off the highway.) This bridge is, in itself, an important historical and strategic piece of WWII real estate, and bears a plaque to that effect. Both the Germans and the Allies at various times attempted to destroy this bridge by bombing. The bridge still stands. The town of Pontaubault, however was leveled!

As you can see, kayakers and surfers enjoy taking advantage of the arrival of the tidal bore for a little fun.
Below, viewed also from the bridge in Pontaubault, as le mascaret passes, we get a little better perspective of the power of this phenomenon.
More pics coming of possible places to visit.