RedactedNarrative: Operator was on a moored vessel on a mooring when he turned on the water heater and it began to smoke around the insulation that covers it.  He saw a flame.  He used 2 dry chemical fire extinguishers and then went above deck and tripped and fell over board and clung onto an inflatable boat.  He breathed in smoke and dust from the dry chemical devices.    He went back to the vessel and slept on it overnight.  The boat was covered in dry chemical from the extinguishers.   The damage was contained to the water heater only.