Second pressurized water tank?

Naddy had a big pressurized water tank in the front of the trailer under the Gaucho. We were however, surprised to find a second water tank - at least I assume that this is what is pictured here - under the bunk bed on the roadside. The belly pan was also modified to allow installation of this tank below the sub floor. Not sure this was a good idea since the floor was totally gone in that area.

The water heater. I would like to say it is the original water heater although I am not sure why it was installed somewhat unorthodox. The access hatch was modified and in order to fit it in, the installer/PO cut half an inch out of the C channel including the rivets that tighten the belly pan and the outer shell to the C channel in that area. Well, something to think about fixing at a later point.
Naddy does have btw yet another water heater tucked into the closet in the bathroom...