You need to ventilate your boat after refueling to disperse any build-up of flammable fumes - especially petrol (diesel is less dangerous). Any petrol fumes sinking into the bilges could be ignited by a spark from an electrical switch, or when smoking.
Fuel vapours will linger in the cabin
Fuel vapours will linger in the cabin
You have a high risk of blowing up you boat.
There will certainly be vapour from the fuel present and lighting of any naked flame could cause an explosion of this vapour.
extinguisher
Unusually nothing happens. BUT a build-up of fumes is possible under the right conditions. That along with an ignition source (engine starter motor etc..) can cause a catastrophic explosion. Use the blower while fueling and before starts IAW your owners manual.
closing all hatches and doors while refueling
Run the ventilation blower for a minute after fueling.
Fire Extinguisher
On the dock and away from the boat
Gas fumes will stay in the bottom of the boat.
On the dock and away from the boat