A better set for Sharpedo may be:
Sharpedo @ Sharpdeonite
Ability: Speed Boost
EVs: 252+ Atk/ 252 Speed/ 4 Def
Nature: Jolly or Adamant
- Waterfall (flinches, 80base power physical move) If you insist on Hydro pump, keep the 4 SpAtk, or possibly add more.
- Crunch (stab, 80 base and then...