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.
Dig it out in the underground.
buy it in celdon city
Its evolve to Vaporeon from eevee
You Need A Waterstone.
Espeon: Evolve at day Joteon: Thunderstone Vaporeon: Waterstone Flareon: Firestone Leafeon: Leafstone Umbreon: Evovle at night Glaceon: Evovle at ice cave (i think)
You can buy them at Celedon's Department Store.