Barrel Water

How can you make a hot water heater for a hunting camp using a 55 gallon barrel?

I heard that you can use copper tubing coiled in a 55 gallon drum, but how? I understand that I will have to place hot coals in the barrel for the heat source, but I don’t understand how to construct the barrel where it will work. I need the barrel to fill up with water from a systern and the barrel will be gravity fed. Any help will be greatley appreciated.

Would not recommend this Project
electrical injury cost for barrel is not worth it
need steel barrel

Rain Barrel filling with water envirosponsible