How do i beat crasher wake in pokemon platinum with my party?

Crasher Wake uses Water type Pokemon so, that's your problem. Use a Gr type and you can beat him. You could really use Gr or, Electric but, I beat his Gyrados with a Roserade level 47, moves: Leech Seed, Mega Drain, Magical Leaf and Poison Sting. His Gyrados is the STRONGEST Pokemon he has so, that's the one you need to worry about. Take it out and since the other Pokemon are weaker than Gyrados and you take it out, Handleing Something weaker shouldn't be that hard. I hope this helps. BYE!!!