whell horsea can be found in the misty map but itsrealy REALY rear and it can b found in Underwater map in INDIGO WORLD......but you can allways trade, but you need a groudon,palkia ho-oh,suicune or eny other cool pokemon.....
ok you can find horsea at misty map and you can find him on the underwater map also.
HOW GET A HORSEA ON POKEMONINDIGO.COM
A Horsea will be found if you get a good rod and look for a lake or river.
you get horsea on route 226
You can catch Horseas around level 10-13 in The Underwater Zone (Indigo World Map).
Fish on routes 132 133 134 with a super road they are very commen so they wont take long to find #
You can find Horsea at Vermillion City or Routes 10-13
I dont believe you can get a horsea in Pokemon Arcoiris but you can get its evolutions evolution,Kingdra on the first route
it depends on the system
Use a good rod where you can find horsea use your pokedex if you seen one already.
in whirl islands you have to have surf
In Route 12 and 13.
Entei can be found in Nimbasa City in Pokemon Indigo.