You can buy them at Celedon's Department Store.
(firered) get eevee in celadon and give it waterstone.
You must evolve the Eevee you get from Celadon City with a Waterstone.
For which game? Pokemon Red Pokemon Blue Pokemon Yellow Pokemon Gold Pokemon Silver Pokemon Crystal Pokemon Sapphire Pokemon Ruby Pokemon FireRed Pokemon LeafGreen Pokemon Emerald Pokemon Diamond Pokemon Pearl
Exchange Blue Shard with the Waterstone. You'll find waterstone in Abandoned Ship, too.
Poke'athalon
I don't have those games, but is it possible that, as in Firered, that you get them in celadon city's big store? Or like Pokemon gold that you get it if you show Bill a nice water Pokemon (don't remember which it is, but it was oddish for the grass stone).
only vapreon
lombre and staryu.
I know poliwhirl will evolve to poliwrath and that shelder will evole to cloyster with the waterstone
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.
lombrea, evee, poliwhirl, shellder, and staryu. some of these can only be found in firered and leafgreen so you will need to trade. that's all I can think of.
Dig it out in the underground.