Slowbro’s tail has a Shellder firmly attached with a bite. As a result, the tail can’t be used for fishing anymore. This causes Slowbro to grudgingly swim and catch prey instead. When a Slowpoke went hunting in the sea, its tail was bitten by a Shellder. That made it evolve into Slowbro. An attached Shellder won’t let go because of the tasty flavor that oozes out of its tail.
Pokédex entry #80
slowbro in Pokémon GO
It's possible to hatch slowbro from an egg?
No, slowbro can't be hatched.
Which are slowbro’s strengths and weaknesses?
slowbro is a psychic and water type Pokémon. psychic type pokémons are strong against fighting, poison, ghost pokémons but weak against bug, shadow pokémons. water type pokémons are strong against fire, ground, rock pokémons but weak against water, grass, dragon, electric pokémons.