Which action should be taken immediately upon discovering a fire on board?

Upon discovering a fire on board, the immediate and most critical action is to sound the alarm. This step alerts the crew and passengers to the emergency, prompting a rapid response and evacuation if necessary. Sounding the alarm ensures that everyone is aware of the situation and can take appropriate action, such as following emergency protocols and utilizing firefighting equipment.

While attempting to extinguish the fire, closing hatches, or turning off electrical appliances are important elements in managing a fire, the priority must be to inform everyone on board. Without sounding the alarm, the risk escalates as untrained personnel may unknowingly enter a hazardous environment or fail to evacuate. Emergency protocols are in place for these situations, so alerting the crew to the fire is the essential first step in managing the emergency effectively and safely.