Answer:
You mean SWAMPERT, yes? So here's the deal... It all depends on the nature! Look at this list...
MODEST, TIMID, MILD, RASH: Look for special moves such as Hydro Pump, Surf, Ice Beam, Mud Bomb, Focus Blast, etc.
ADAMANT, JOLLY, LONELY, BRAVE, NAUGHTY: Physical moves are the ones you want, like Waterfall, Ice Punch, Earthquake, Brick Break, Aqua Tail, etc.
ANY OTHER NATURE: Look at the stats now. If they are equal, choose either physical or special. Hope this helps!