To catch Feebas you must go to the northern area of mount coronet where there is the fog. Use defog and then make your way into the water. Use surf and then take out any rod and start fishing every in the water. Feebas is the hardest Pokemon to find on Pokemon platinum so it will take forever to catch it. If you kill it by accident or it runs away during a wild battle don't worry. Feebas usually doesn't move around to different spots in the water. Lastly, you can use your pokedex to find it if you can't understand this and have a good team with you because you will be harassed by Gyarados and Zubat a ton of times.
it is found in mount coronet
its between lake valor and sunnyshore city
You have to level up feebas with maximum beauty, which can be done by giving it poffins. It can evolve at any level as long as it has maximum beauty.
You can find a trainer with a feebas on route 222 to the left of sunnyshore city.
Pokemon #138 in the Sinnoh Dex is Feebas, which can be found under the ownership of a fishermannear Sunnyshore City.
mt.coronet
on the left of sunnyshore city. a fisherman has feebas
fisher man
mt coronet
Feebas
mt corenet
feebas
Fishing in Mt. Coronet
yes
someone on route 222
a fisher man on route 222 has it
theres a hidden lake in mt.cornet