As trachy said, Aqua Tail is the best choice, as Hydro Pump has no point as its bad accuracy and your attack is higher than defence.
Another Idea is to evolve it too. LV. 42 is pretty high, and it doesnt learn many more moves unless you evolve it to Samurott.
As for your other moves, Revenge isnt big on Oshawott, as it isnt STAB. Replace it for a status move like Attract. (Found on the last street of Castelia City on 47f.)