I have bought Sharki #80 build in 1982 in April this year and I'm still working on it to make it a little bit better.
There are two systems to make warm water and this is not state of the art as for today. I have found a warm water boiler in the engine room to make warm water with the engine cooling system. So it works only when the engine is running. Another heater with 220 Volts connection is below the kitchen sink which works when shore power is available.
Modern warm water heaters as of today uses only one device like the boiler shown here from Quick. They get their heat from engine cooling system and/or from shore power as well. I will change this next year.
Actually I have changed already the Jabsco WC to the better Lavac Vacuum toilette and next I throw out the old Frigoboat fridge which has two compressors: One with shore power 220 volts and one compressor attached to the engine. I will build in a Coolmatic fridge with 12 volts only. My batteries are strong enough and the Sharki has 3 alternators.