Surf-more reliable than hydro pump.
Ice beam-Covers those grass types.
Aqua ring/agility/yawn-A good support move will help. Yawn is good to either get a sleeping foe, or force a switch.
Mud slap-cheap move, most of the good electric types have low defenses, so this can do a bit of damage, while protecting piplup with low accuracy, of course, you'd probably switch out Piplup anyway.