This Pokémon only spawns in areas with the natural=beach tag. As a result, some players have been adding beaches near their neighborhoods to make it easier to catch the Pokémons. In fact, I've already come across Pokémon GO player blogs that actively encourage other players to edit the OpenStreetMap data directly to facilitate easier catching.
@rtnf Niantic uses outdates map data, there's no confirmation that newsly mapped beaches affect pokemon spawns. Basically a few players encourage thousands other playes to vandalize the map, and a company is held accountable.