I kill it with extreme prejudice. It's a very invasive plant, and can almost visually spread by the day. If you go by the recommended herbicide options, be sure and treat it as per the instructions. If your mix is too hot, it'll just burn the tops off, and not kill the roots. Popups several feet away can continue after the treated plant is long gone. I've had luck controlling it with both liquid and granular treatments.

Water Pennywort

AL