With Sharpedo added to your arsenal of Ride Pokémon, you may be wondering if there are any previous areas where it might be useful. Of course, the answer is yes! (But only two places.)
Whenever you have a spare moment, let Charizard fly you to Ten Carat Hill on Melemele Island. If you haven’t visited Ten Carat Hill yet, fly back to your house instead, then travel south. Either way, head over to Professor Kukui’s lab, then swim south-west from the shore–naturally on Sharpedo’s back. Keep going until you exit to the next area.
Beyond, follow the south side of the cliff west. As you approach the corner, there’s a line of floating boulders surrounding a cave entrance. Let Sharpedo deal with the boulders so you can enter the cave. Inside, you’ll emerge towards the south-west corner of Ten Carat Hill’s interior. Follow the subterranean stream north-west.
On the other side, you’ll emerge in a secluded cavern, with a dangerous item sitting in the very center: TM64 Explosion. Before you start feeling claustrophobic, leave the cave the way you came.
Next, fly to Big Wave Beach, also on Melemele Island. Upon arrival, head for the southernmost tip of the beach and enter the Sandy Cave. If you came here earlier with Lapras, you could have obtained a Big Pearl from the center of the cave. This time, continue north-east from the center and smash the boulders to the right with Sharpedo.
Afterwards, follow the water south back to dry land. Further south, there’s a Light Clay sitting next to the ledge that leads back to the cave entrance. Once you’ve carefully made space for it in your bag, hop over the ledge and exit the cave. From here, you can return to your adventures without further worries!