in Pokemon diamond it is in were the elitle four thing is outside in the water. and that route after it were shaymin is. but you have to use a rod.
In the wild grass you can find: Lillipup,Patrat,Pidove(i am not sure) and less likely -Purrlion In the water: most likely Basculin
You can get a Seel in Pokemon Pearl by finding it in the water on route 226.
Manta (any thing that has to do with water or the pokemon)
When you are on route one go surf on the water and go around to the next piece of land. You can find them in the grass. FYI they are called Watchogs
Route 18.
You have to go through hole in the sky scrapper!
in Pokemon diamond it is in were the elitle four thing is outside in the water. and that route after it were shaymin is. but you have to use a rod.
At the farthest and lowest point toward Drivtveil City.
Go to Route 6 and fish in rippling water.
On route 1 by surfing into water ripples (similar to shaking grass but on the water surface)
In Route 1, use Super Rod or wait for rippling water.
In Route 4, when you fish in rippling water. There's a 60% of it being Relicanth.
Go to route 4 and fish by the water, and you should eventually catch one
get a pokemon that knows surf and go to the water at route 1.keep going until your on route 17 and keep surfing around.this works i white too
you get waterfall on route 18 after you get surf, route 18 is the water next to route 1,you just a little bit btill u hit land then you search for it
The water route is the Danube.