Thanks to a high attack stat, especially with the Shadow variant, we can actually sneak in a good number of wins, including against Mamoswine ... There is a shiny Oshawott in Pokémon Go.

Shiny Zekroms are rare ... Landorus (Therian Forme): With Mud Shot and Earthquake. Ice-type Counters: Mamoswine: Utilizing Powder Snow and Avalanche. Weavile: With Ice Shard and Avalanche.