GALVANIC ISOLATORS
Recent interest in damage done to boats due to the 230V shore mains has highlighted the need to fit a galvanic isolator to your boat.  In order for modern boat builders to comply with modern CE standards such as EN ISO 13297  they must fit the shore earth wire to your boats bonding system which is also connected to the hull /anodes / fuel tanks /engine blocks / shafts / propellers / stern tubes /rudders / rudder glands / water intakes / etc. This ensures that any 230V mains faults will operate the R.C.D on the boat in order to save your life.  The down side of these standards is that electrically speaking your boat is now connected to the rest of the boats in the marina and any other metal structures in the area. Electrically speaking they become one and the same.