This is part 35 of my ongoing walkthrough for Pokemon Diamond/Pearl.
In this video, I take on Pastoria City's Crasher Wake, the master of water type pokemon.
Wake shouldn't be too hard to defeat if you have the right type of pokemon, his levels are actually the same as Maylene's, so that shouldn't be too much of a problem. Finding his weaknesses are the most efficient way of beating him.
Gyarados Level 27
(Weak to Electric, Rock)
Quagsire Level 27
(Weak to Grass)
Floatzel Level 30
(Weak to Electric, Grass)
After defeating Wake you will receive the Fen Badge, the fourth badge in the Sinnoh Region, it let's you use Defog outside of battle. As a bonus reward, Wake gives you TM 55 for Brine, a pretty good water type move.