Which of the following is NOT a common extinguishing agent found aboard a vessel?

Cryogenic fluid is not a common extinguishing agent found aboard a vessel. Typical firefighting agents used on vessels include water, foam, and carbon dioxide (CO2).

Water is a versatile extinguishing agent that is effective on many types of fires but is used with caution, particularly on flammable liquid fires. Foam is specifically designed to suppress flammable liquid fires by creating a blanket over the flames that prevents oxygen from reaching the fuel. CO2 is also commonly used on vessels because it displaces oxygen, suffocating the fire while causing minimal residue.

In contrast, cryogenic fluids, while they can theoretically extinguish fires through extremely low temperatures, are not practical or standard extinguishing agents in maritime firefighting. Their handling and storage present significant risks and challenges that make them unsuitable for routine use on board.