When you go in the cave, If U Have Hm waterfall You Use It .. Go Near It And Press A They will Ask You Want Anot.. If You don't have, U Need To Go To The holes.. Don't Go To The Holes Witch Is The 4 holes that is stick together.. After That u go to the front one u try it out then u can get to the waterfall HM.. But 1st U must Slide On The Ice Sliding Tingy