Turtle Cove is an area in Johto that is home to the starter Pokémon Squirtle.

To get there, head to distant isles (Three Island), and take a trail that leads up all the way to a peninsula. From there, you will find another water route. It looks like the one to distant isles, but isn't. Eventually, you will reach turtle cove.

Wild Pokémon

Pokémon Method Rarity
Pokemon Geodude Geodude Walking Common
Pokemon Zubat Zubat Walking Common
Pokemon Sandshrew Sandshrew Walking Common
Pokemon Tentacool Tentacool Surfing Common
Pokemon Magikarp Magikarp Fishing Common
Pokemon Goldeen Goldeen Fishing Uncommon
Pokemon Horsea Horsea Fishing Rare
Pokemon Shellder Shellder Fishing Rare
Pokemon Staryu Staryu Fishing Very Rare
Pokemon Squirtle Squirtle Walking / Fishing / Surfing Extremely Rare