cardboard

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=11&cad=rja&uact=8&ved=0ahUKEwjsyIzmqMPTAhXC7CYKHZF_ALYQFghrMAo&url=http%3A%2F%2Foutlivetheoutbreak.com%2Fcardboard-box-water-tank%2F&usg=AFQjCNGuWpmhFroWNSbTrxYp80fClua4Gw&sig2=NlyYHwQt-1-MGtJwMJGcsA Basically, take a cardboard box (I...