What action does a ship take when it displays the flag 'Mike'?

When a ship displays the flag 'Mike', it signals that it is taking on or discharging a hazardous material, specifically underscoring the need for caution in that area. The flag 'Mike' is denoted by the signal flag which is primarily associated with the medical guard duty message, denoting that medical assistance may be necessary and that the ship is prepared to provide immediate medical response. This is known in maritime communication as an indication that the vessel is capable of dealing with medical emergencies onboard.

Understanding this context is crucial for maritime operations, as consistent and clear communication through flags helps maintain safety at sea. While other flags serve entirely different purposes—like signaling a 'man overboard' scenario, a boat recall, or indicating a fuel transfer—the 'Mike' flag is specialized for medical readiness, reinforcing the importance of recognizing specific maritime signals and their meanings during operations.