DO NOT USE ELECTRIC SHOCK!!!!!! I am serious. The outcome of sending power into your pool will be worse than letting them poop in your pool. When electricity archs underwater, it will split the water into hydrogend and oxegen(electrolysis). That isn't goint to be your problem though.
When the water is splitting, it will also separate the chlorine, iron, copper, zinc, and all of the other chemicals and minerals in your pool. While thoughs chemicals and minerals are floating arround, they will also(very quickly) corrode your anode and cathode. If the anode and cathode are copper, then you will get coperoxide brewing in your pool.
So, what i am getting at, is; by the end of the week, your pool will have approximately 1cm of green sludge floating on the top. Yes, this will get rid of your duck problem, but it will also create a health hazard(not kidding).
You may be asking yourself; "Why should i trust you?". Well, i have done some experimenting with electrolysis and fuel cells. I will just simply tell you; I got very, very sick from some of the biproducts(I'm not sure what will happend with chlorine in the water, but it probley won't be pretty). Please, for your safty, and the safty of others; DO NOT USE A SHOCKING SYSTEM.