At the pokeathlon dome as a prize on Wednesday.
the pokeatlon on Wednesday
Pokethan.
Staryu.
use the water stone
You need a Eevee and a water stone use the water stone on eevee! Simples!
go to the pokeathlon dome and get 2500 points and trade them in for a water stone
A water stone
You can get a water stone at the Pokeathon at the prize exchange or you can get it if you come in first in the Bug catching contest.
Fire Stone Water Stone Thunderstone Leaf Stone Dusk Stone Sun Stone Moon Stone Dawn Stone
You buy it with points at the Pokeathlon Dome.
Your best bet would be to get points in the pokethlon and exchange them for a water stone at the exchange counter farthest to the right.
WHEN YOU GO THE POKÈLTHON YOU HAVE TO HAVE 2500P AND YOU GO TO YOU'er right there is a lady and that's how you get a water