"I am taking in, or discharging, or carrying dangerous goods."
Originally used by the Royal Navy specifically for military explosives.
U.S. Navy Meaning:
Bravo at Dip: Bravo flag is located 3⁄4 way up toward the point of the hoist. On the delivery ship, it means, "I have temporarily stopped supplying." On the receiving ship, it means, "I have temporarily stopped receiving."
Bravo Close Up: Bravo flag is at the top of the hoist, touching the point of the hoist or as high as it will go. On both ships, it means fuel or explosives are being transferred.
Bravo Hauled Down: On both ships, it means delivery is complete.