yes, go in the cave that's under the bike brigde
Wayward Cave
it will be the female Pokemon
you can get diagla on dimond
in a cave under the bridge by wayward cave on pearl
Wayward Cave on route 216
you cant he is only in pearl, diamond
A rare Pokemon to get in Wayward Cave and totally worth while in my opinion is Gible. Gible is the 'baby' version of Garchomp.
gible evolve to gabite at level 28 and gabite evolve to garchomp at level 48
go to wayward cave b1f near oreburgh city
To obtain a Gible on Pokemon Pearl and Diamond, go to the secret place at Wayward Cave, which is under the cycling bridge, just walk around till you encounter one! It's not very complexional at all.
you run along the walls until you find gible, or if its not the secret entrance, you go deep into the cave and find gible
You can find a Gible somewhere along Route 206 which is below Eterna City and above Oreburgh City. I hope this helps in you're still looking for a Gible.