You can find water stone from the following places:
National park (if you win bug catching contest you have chance to win it)
Route 42 (pokegear phonecall)
Route 25 (show staryu to Bill's grandfather)
Seafoam islands
You can also buy it from pokeathlon dome.
For more info click link below.
fiserman tully will cal you that he find something you have to go to him en he will give you the waterstone
The easiest way is to buy it at the Pokeatholon on certain days. it's about 1000 points. The precious stones are really hard to find. Some days there will be water stones, fire stones, etc. etc. just like some people can give you stones, but the pokeatholon is the best way to go (go left inside the first barrier to the National Park).
Chat with our AI personalities
Exchange Blue Shard with the Waterstone. You'll find waterstone in Abandoned Ship, too.
You can find it in Pokemon Platinum, Pokemon Crystal, Pokemon HeartGold, and Pokemon SoulSilver.
You can only find Skarmory in the Pokemon SoulSilver version.
Meowth are Pokemon SoulSilver-exclusive Pokemon. In SoulSilver, they can be found on Routes 5-8, 38 and 39.
You'll need to trade for it, because evolving Feebas will be impossible in Pokemon HeartGold and SoulSilver.