This move set takes total advantage over hydration, thats where the name comes from. Start off with rain dance and rest off the major damage while using either surf or grass knot which can be replaced by Ice beam.
Maxing HP and SP ATK ev's makes it harder for them to knock you out and easer to knock them out. Leftovers is used to keep off minor damage givers like sandstorm or making the battle last longer, can get replaced with damp rock for rain dance to last longer...