Detailed Information regarding Wimpod’s Location and the strategy to encounter it in Pokémon Sun and Moon.
Wimpod an be found near the rocky stretch at Route 8.
As you arrive at the rocky stretch, you will notice a shadow of a Pokemon. If you attempt to approach the shadow by foot, even by running, it will run away.
Use Poke Rides that increase your movement speed such as a Tauros to catch up to it.