Having been in plastics for 35 years, the water style or stackables look to be just blow molded HDPE where as fuel jugs are multi layers for permeation and UV. Here is a decent setup I found, however wrong color, There is also a 6 gal version I seen but have not found where to purchase.

http://discountmarinesource.com/p-68...FRaewAod_KIDRA

http://www.boatstore.com/scepter-857...FYuMaQodSCkKMA