[sseaman]

you can go with the tarp and tube idea, make a cut length wise down the tube, and the end of the tarp staying there attach a pipe to it, this will keep ip from coming out of the tube, and give you something to wrap the tarp around. then stick inside the tube and cap the end. Position the tube with the slit down, and you dont have to worry about water staying in. Ofcourse this idea is in my head and hasnt actually be tried, though it should be shortly.