uhhh... it looks like a freshwater tank to me... TRAITOR!!! lol... it is really cool!
I saw a truck like that once, only it was a pic on the back of the semi... you know, on the door. And it looked like the door was open, and there were bread rolls everywhere. I freaked out at first cause i though they were all going to fall out of the truck, but then i realized it was just a really cool paint job/sticker of some sort...