Pokémon S10 E47 Sandshrew's Locker!

"Gotta catch 'em all!"

A girl named Mira offers to use her Abra to teleport Ash, Dawn and Brock to Hearthome City, but it takes them to a lake instead. Mira explains that she needs their help to retrieve her submerged Sandshrew, which an ornery Gyarados fiercely guards.