I think you get it in Sunnyshore City from Jasmine at the top edge of town. If she doesn't give it to you, I'm still sure it's somewhere in Sunnyshore. you have to beat the Sunnyshore gym leader and then talk to Jasmine and she'll give it to you
it is waterfall.
You can get the HM waterfall in Pokemon Diamond and Pearl by beating the 8th gym leader and talking to Jasmin by the little beach. She will give it to you.
No you don't.
To my knowledge i don't think there is a waterfall in Pokemon yellow and it is quite irrelevant to the storline if there was one. If you mean a HM named waterfall...i think your on the wrong game, only pearl and diamond have waterfall HM...i think. There are only 5 HM's in Pokemon Yellow Flash, Cut, Fly, Surf, Strength.
Get the HM Waterfall and then when you find one, face it and press A.
you get the hm waterfall and then teach it to a Pokemon then if you have pearl dimondor platinum you go to mt cornet but for soulsilver and heartgold you go to mt mortor ,mt silver.
once you have the beacon badge talk to jasmine at the place where there's sand. She'll give you the HM waterfall.
first get the electric gim bage after that talk to that girl in the beach in sun shore city then she will give you hm waterfall
You get the HM waterfall in the same cave you get Kyogre
You have to get the HM Waterfall, which can be obtained in Sunyshore city after beating the last gym.
You get HM Waterfall at the end of Route 18 on the strip of grass in Pokemon Black.
the HMs are strengh,defog,waterfall,surf,rock climb,rock smash,and fly