The man knows...
But anyway, apart from Gyarados, i recommend this, based on the last gym you beat:
You got an Azurill... I don't need to say anything, Azumarill is TOO powerful if you got that Huge Power going... Seriously, consider... and if you decide against Azumarill... think again...
You know, Sharpedo is frail, but if you get the Speed Boost going, that STAB Crunch is going to hurt... So, you should look into that...
Unfortunatelly, if you got Sharpedo, that means you joined team Aqua right? if you joined Team Magma, you could get a Chinchou and get a Lanturn (And i LOVE LANTURN), but yeah... no chance...
I'm just going to say: Keep playing... there's better water types in the future, so keep at it!