Electric Camping Lights Can You Use The Shower In A Touring Caravan Without Electric Hookup?

Can you use the shower in a touring caravan without electric hookup? - electric camping lights

This may seem a silly question, experienced caravanners, but we only have a caravan of age, with or without a hot shower. Often, camping and recreational lights the battery is disconnected and the pump cold water into the sink. Now we plan to find a modern truck with a shower, but I do not know how it works. The water is heated with gas? or make it imperative that connection. would be very grateful for that statement.