you have to get all the gym badges in kanto
Hm08 is rock climb not waterfall. Hm07 is the move waterfall
In Pokemon HeartGold and SoulSilver Versions, HM08 Rock Climb is not needed to get to Seafoam Islands, HM03 Surf is though.
There is no HM08 in Pokemon Crystal. Pokemon Crystal has only 7 HMs that are available to use.
HM08 Rock Climb is given to you by Prof. Oak once you have all 16 badges.
There is no HM08 in the original Pokemon Gold game however in HeartGold HM08 is Rock Climb which you can get from Professor Oak in his lab in Pallet Town after you've beaten his Grandson; Blue who is the Gym Leader of Viridian City.
You go to Steven's house in Mossdeep city. He's northwest of the Pokemon Center. When you enter, he'll give you HM08. HM08 (Dive) is exclusive to Pokemon Ruby and Sapphire and is obtainable in Mossdeep City from Steven who resides there. Steven
There are only 7 HMs.
You do not need HM08 to reach Cinnibar Island. You do, however, need HM08 to search Cinnibar Island. Without HM08, all you can do is use the Pokemon Center.
There is no best Pokemon on Pokemon HeartGold.
there is no Pokemon Mansion in Heartgold.
there is no hm08 in leaf green
They are not in Pokemon HeartGold