When you shock fish they do not "float to the suface" the electric current makes them spasm and they are forced to swim towards the source, if the current is strong enough.

If you are shocking a small stream you can use a small shocker because the fish have nowhere to run. But in a pond the fish feel the weak current and simply swim away.

The small shockers I have seen generaly run on a tiny gas powered generator. The larger ones require a boat. The largest one I have ever used was towed on a tiny bass buddy boat, and powered two wands. The stream we were shocking was around 5' deep at the deepest and had very low conductivity. We had minnows swim next to our wands and show no effect.

I would look for a "toaster", thats the unit that regulates the electricity, that you can attach to your own generator. I wouldn't trust a battery powered shocker, and never in a pond.