What warning should be given when submarines are operating in the area?

The use of the NE2 code flags is a recognized maritime signal indicating the presence of submarines operating in the area. The display of these flags serves as a warning to other vessels in the vicinity about the submarine's activities and the potential for submerged operations, which may require them to exercise caution. The international maritime community recognizes these flags as a clear and effective means of communication regarding underwater navigation.

This warning system is vital for ensuring navigational safety and preventing accidents, as other vessels may need to alter their course or speed when near a submarine. By exhibiting the NE2 code flags, submarines can effectively communicate their presence and operational status to other mariners.