Jeremy,
Your coach has a Seaward electric/heat exchanger water heater. It sounds like the magnesium anode rod in your water heater has not been changed like it should have been, and the aluminum inner tank has developed a leak from electrolysis.
If the tank is leaking, you can either remove the heater and replace the tank, or replace the entire heater. Replacing the entire heater will probably be about the same cost as the tank only when you consider labor cost. Check the model number of your heater, and you should be able to find a direct replacement at most marine parts suppliers since the heater was originally designed for boats.
Remember to watch the anode rod, and replace it when necessary so that this does not happen again.
Gerald
