Getting Water Spout Blastoise will require chain breeding. Breed a Male Wailord knowing Water Spout and a female Octillery. Keep breeding until you get a male Remoraid knowing Water Spout. Then breed a female Blastoise with the male Remorade/Octillery. As long as Remorade/Octillery doesn't have any other egg moves that can be passed onto Blastoise you should be fine.
