in whirl islands you have to have surf
You can get a Horsea in Pokemon Silver by finding it at the Whirl Islands.
HOW GET A HORSEA ON POKEMONINDIGO.COM
you get horsea on route 226
You can find Horsea at Vermillion City or Routes 10-13
Level 32
I dont believe you can get a horsea in Pokemon Arcoiris but you can get its evolutions evolution,Kingdra on the first route
By fishing or surfing in the whirl island caves
it depends on the system
Use a good rod where you can find horsea use your pokedex if you seen one already.
In Route 12 and 13.
Nobody knows lol.
You can find Horsea around Whirl Islands, and I suppose you can evolve it from there.