Breed a female Mamoswine(or any Pokémon from the evolutionary line)with a male Beartic that knows Icicle Crash.
Once you have a female Piloswine that knows the move Icicle Crash, breed it with a male Seel/Dewgong that knows Icicle Spear. The resulting offspring should know both Icicle Spear and Icicle Crash.
Hope I helped
Edit: To get Icicle Spear on Seel, it also needs to be bred. Breeding Icicle Spear on Seel is quite hazardous, but isn't too hard. Here is Seel's egg move page. You can also utilise Smeargle's Sketch to get a compatible parent.