In the cave of origin which is in sootoplis city.
HM 07 in emerald is waterfall
you recieve the hm waterfall after you have deafeated the elite 4
The way you get waterfall is by trading the waterfall HM from Fire Red Version or the other Version that have waterfall HM ( you can trade with a link cable or wireless adaptor)
Get the waterfall hm!
the last one because you need waterfall to enter the elite four
you get it at cave of origin but you have to beat the gym leader of sootopolis city to use it on the waterfall to ever grande city
try using a Pokemon w/ the hm waterfall, isn't that obvious...
The HM Waterfall can be found before battling the 8th Gym in Sootopolis either by Steven or Wallace (I forgot)
Go to Meteor Falls and catch a Bagon
you get HM waterfall on route 18
there is no hm waterfall that i know of
You get hm waterfall(I can't remember how:()and beat the sootopolis gym leader(8thgym)