You can't in Ruby, Sapphire, or emerald, you have to look for them.
you cannot buy a water stone
none , u have to buy the water stone
you cannot buy water stones you can get them with the hunter he lives in a house in the sea
Nowhere.
You can buy one from the PokeMall.
buy it at the pokeathelon dome
you buy them at celedons department store.
You buy it with points at the Pokeathlon Dome.
In fire red you can buy it at celadon city.
Yes in fact you can get dozens if you trade with firered or leafgreen because they can buy water stones all they need to do is trade you a Pokemon holding the water stone and when you get it just take the water stone from it!
Sun stone: win bug catching contest or buy at pokéathlon shop Moon stone: behind tohjo falls Leaf stone: buy at pokéathlon shop or win bug catching contest Fire stone: sea foam island BF2 Water stone: route 17 water surface Dawn stone: pokéwalker route treehouse or buy at pokéathlon shop on 2 days each week Dusk stone: same as last, but at different days of week Shiny stone: win at bug catching contest Hard stone: goldenrod department store BF1 Ever stone: geodude may be holding it when you catch it Plain stone: buy at battle frontier on tuesday Dull stone: buy at battle frontier on thursday Guard stone: pokéwalker route dim cave
U buy it at goldenrod dept store