I keep a bilge pump rigged up with a length of hose, and a wire long enough to reach my batteries with a set of alligator clips. If I need to fill my live well, I toss the pump overboard, run the hose to my livewell, and hook the clips up to my battery. Fill the livewell, then unhook the pump.
A set-up like this would be handy on any boat. If a livewell pump failed, you could fill your livewell, you could pump your livewell out if you needed to, and you could use it as an extra bilge pump if you had an emergency that your regular pump couldn't handle. It can also be used to pump the water off your boat cover.