You can buy one with Athlete Points at the Pokeathlon Store on some days, or you can get a Waterstone from Bill's grandfather after you show him a certain Pokemon.
I know poliwhirl will evolve to poliwrath and that shelder will evole to cloyster with the waterstone
At the very end of route 25, there is a house and a guy asks you to see certain Pokemon, show him the Pokemon and he gives you different stones, one of which is a water stone! hope this helps!~
Exchange Blue Shard with the Waterstone. You'll find waterstone in Abandoned Ship, too.
Poke'athalon
only vapreon
lombre and staryu.
Espeon: Evolve at day Joteon: Thunderstone Vaporeon: Waterstone Flareon: Firestone Leafeon: Leafstone Umbreon: Evovle at night Glaceon: Evovle at ice cave (i think)
buy it in celdon city
Dig it out in the underground.
Its evolve to Vaporeon from eevee
You Need A Waterstone.
You can buy them at Celedon's Department Store.