Never had much luck with covers for dinks stored in the water. PITA's and don't work well. I just rigged up a bilge pump/switch combo mounted on a piece of 1/8 acrylic with a small 12V dry cell battery from EPO in our area. It's the kind of battery used in alarm systems and the like. You have to bring it in once a month or so and put it on a little charger purchased at the same time. I think I put the entire system together for $75 or so.