We had an old Winnebago Chief MH with a swamp cooler similar to the turbo kool. I don't remember the brand but it was designed specifically for an RV and worked off of 12V and drew water from the MH freshwater tank.
As others have written they only work well in dry climates. It will not keep the entire RV cool you need to sit right where the air flow from the swamp cooler is in order to stay cool. In the winnie the airflow pointed towards the dinette area so that's where the 4 of us would sit to be as cool as possible in 80 plus degree outside heat.
All of our RVs since have had air conditioners...no more swamp coolers for us.