Where is a water stone in heart gold?

Answer 1

Theres a number of ways to get ahold of the stone, unfortuantly none of those ways include purchasing.

Probably the easiest way is to humor Bill's grandfather in his annoying little game. Find the pokemon he asks for and show it to him he will reward you with the stone type matching the pokemon he shows you. I think you need a staryu to get the water stone. (only works once)

Another low stress method is Route 42 Fisherman Tully, Defeat him and collect his phone number. When he calls you for a rematch beat him again and he will give you a Water Stone as a reward. His level 19 Qwuilfish shouldnt be a problem but rematch callers can be quite unpredictable so there really is no telling how long this could take. (genuinely not sure if this will work more than once. I'm leaning towards no)

You could try the Bug Catching Contest on tuesday thursday and sunday, first prize has a 1 in 10 chance of being a water stone. Your odds are so terrible I wouldnt count on this one. (Works more than once, but can only work after you get the national dex)

If your ok with distances then there is a water stone just lying around in the Sea Foam Islands, its near the lower left portion of B2F (downstairs in laymans terms). (only works once)

If you have a staryu and a pokewalker and have traded a pokemon over the GTS (global trade station located in Goldenrod) Then you can pick up a water stone randomly while walking in the Beyond the Sea Course. the stone is kind of rare so I wouldnt get too jumpy about this method either. (Unlimited Supply)

Participate in Events at the Pokeathlon Dome and work up 2500 pts. The water stone can be purchased only on Wednesday. (not sure if this supply is unlimited but I think its safe to assume that it is)

Unfortunatly those are the only methods I can think of combined with the only ones available on Bulbapedia, if your going for a 100% pokedex it doesnt bode well.

Answer 2

Well, if you've got the game I think you have, you can go to the Athlete Shop in the Pokeathlon Dome daily to see if they have it (it will take 2,500 Athlete Points.) If it is not the game I think you have, just look for Pokeballs on the ground. Or if you have the new Heart Gold, you can do both. But I think there isn't one in a Pokeball.