I had to take the kids to Walmart yesterday to buy goldfish. The bags Walmart put the fish in are really neat. I asked and they gave me a few extra bags. The bags are of a different type of plastic than most plastic bags. They seem more puncture resistant and unlike many of the bags I have read about people using, they are made to carry water. You do have to tie off the top with a twist tie or rubber band. I would guess that the bags would hold 1/2 gallon of water if filled up. They are shaped like a loaf bread sack. Give them a try,
David Enoch