The correct answer is fire extinguisher.
Before someone starts to fuel a boat there should be fire extinguisher.
When a person is fueling the fuel might overfill and spill the fuel into engine or to passenger compartment and this can increase the risk of fire explosion and if spilling fuel to the water will harm the marine environment that is why a person should have fire extinguisher when fueling.
Some precautions which are taken when refueling are,
1. Refueling should be done on daylight when artificial light is not needed.
2. When refueling a person should not smoke.
3. Portable tank should be refueled in the tank and not in the boat.