Swimming pool repair water storage bag.
Fullsize image: https://diqn32j8nouaz.cloudfront.net...g_fullsize.jpg
https://diqn32j8nouaz.cloudfront.net/pool_water_bag.jpg
Previously:
https://www.homemadetools.net/forum/...3683#post99771
https://www.homemadetools.net/forum/...583#post132523
