HM08 is only in ruby, sapphire and emerald.
on route 217 outside the mans house you will see a pokeball. pick it up and you have HM08
D.I.V.E
There is no HM08 in Pokemon Crystal. Pokemon Crystal has only 7 HMs that are available to use.
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.
HM08 Rock Climb is given to you by Prof. Oak once you have all 16 badges.
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.
When you're hiking up the mountain in the blizzard you'll see a house with a Poke Ball behind it click it, and it will be hm08 better known as rock climb.
prof. oak gives it to you i think
you have to get all the gym badges in kanto
there is no hm08 in leaf green