How do you use Waterfall in Pokemon Crystal?

AnswerOnce you have taught your Pokemon the HM Waterfall, you must have it in your party in order to use it. Upon reaching a waterfall, Surf to the very edge of where it cascades down. You may find that this takes a while as once you Surf onto the actual waterfall, it forces you back. Once you are facing the waterfall and there is no space between you and it, press A. If the Pokemon who knows Waterfall is in your party, a small message should appear asking you if you wish to use the move Waterfall. Select 'yes' and you will begin to ascend the water.

If you have not obtained the Rising Badge from Claire in Blackthorn City, you will be unable to use this move.