the perfect sharpedo moveset:
Sharpedo @ Choice Scarf
Naughty Nature (+Atk, -Sp Def)
252 ATK/160 SPD/96 DEF
-Waterfall
-Crunch
-Earthquake
-Ice Beam
the reason why it's naughty is because you don't want to reduce its special attack because ice beam. ice beam is there for physical walls like Donphan, Skarmory, Gliscor, Hippowdown and dragons who have lower special defenses. ice beam would OHKO standard gliscor but sharpedo would need to use 3 waterfalls to KO gliscor, so it really makes a difference. ice beam could 2-3HKO skarmory while it would take so many waterfalls to just come close to KOing it.
the defense evs are for surviving an occasional brick break from weavile, earthquake from gliscor, and drill peck from skarmory.