What is required of an investigator during a flooding casualty?

The requirement for an investigator during a flooding casualty involves securing the compartment by checking watertight fittings. This action is critical in mitigating the extent of flooding and preventing further water ingress. By ensuring that watertight doors and hatches are properly sealed, the investigator can help contain the flooding to a specific area, which is essential for maintaining stability and safety aboard the vessel.

Addressing watertight integrity is a fundamental aspect of damage control, as it minimizes the potential for water to spread to other compartments, thereby reducing risks and providing more time for further damage control measures to be implemented. This proactive step aids in preserving the vessel's buoyancy and structural integrity.

Options involving immediate evacuation or waiting for higher authority are generally inappropriate during an emergency situation like flooding, where swift, decisive action is crucial. Initiating a fire watch may be relevant in some contexts, but it does not directly address the immediate concern of flooding and would typically follow the establishment of safety measures. Therefore, the correct answer reflects the most critical and immediate action needed during such a casualty.