You can go to the safari zone, but that is too hard. If you have beaten the game you can get it left of pastoria near the bog
Yes, you follow the Croagunk into the Great Marsh and then catch them.
Safari Zone
Croagunk will attempt to evolve starting at Level 37.
the symbol Pokemon of pastoria is croagunk as shown in the Pokemon episode diamond and pearl #082 cream of the craogunk crop. since croagunk is its symbol they have a sign in pastoria to help you feel as awesome as croagunk by looking like it through the sign in platinum.
The Croagunk is there because of the Croagunk festival, as seen in one episode of Season 11 of the Pokemon anime called "Cream of the Croagunk Crop!".
pastoria great marsh ( not too hard to find )
you can find them in the great marsh
how do you catch a mewtwo on Pokemon platinum
Croconaw evolves at level 38, not by a stone.
you cannot catch the 3 regi's in Pokemon platinum you have to catch them in Pokemon emerald then transfer them to Pokemon platinum. thnx
Croagunk is'nt in fire red. try diamond pearl platinum heartgold or soulsilver.
You can't actually catch him in Pokemon platinum but you can migrate him over to platinum if you have him in another game