Nautical Signal Flags Meaning
Spotting colorful flags on ship masts and yachts? Decode maritime flags from Alfa to Zulu, including diver down (Alfa) and man overboard (Oscar).
Flag Alfa (A)
White and blue swallow-tailed pennant (split tail).Maritime Rule: MANDATORY for dive boats! Passing boats must stay at least 50-100 meters away and idle speed to avoid propeller strikes on scuba divers.
Flag Bravo (B)
Solid red swallow-tailed pennant.Maritime Rule: Flown by fuel tankers while bunkering oil at marine terminals or navy warships loading live ammunition.
Flag Charlie (C)
Five horizontal stripes: Blue, White, Red, White, Blue.Maritime Rule: Universal radio and visual flag response confirming agreement to orders or queries from other vessels.
Flag Delta (D)
Yellow with blue horizontal center stripe.Maritime Rule: Flown by container ships in narrow channels or vessels experiencing partial steering or rudder malfunction.
Flag Hotel (H)
Split vertically: White on hoist, Red on fly.Maritime Rule: Signals to port authorities that a local certified maritime pilot has boarded the ship to navigate harbor waters.
Flag Oscar (O)
Split diagonally from top-left to bottom-right: Red top, Yellow bottom.Maritime Rule: Critical maritime emergency flag hoisted immediately when a crew member or passenger falls into open sea.
Flag Quebec (Q)
Solid yellow rectangular flag ("The Yellow Jack").Maritime Rule: Flown upon entering foreign international waters before health inspectors board. Historically signified quarantine.
Flag Victor (V)
White with red diagonal saltire cross (X).Maritime Rule: Flown by disabled recreational boats or fishing vessels when engine fails or power is lost at sea.
Flag Whiskey (W)
White square surrounded by blue border with inner red square.Maritime Rule: Coast guard and nearby naval hospital ships immediately respond to Whiskey flag transmissions.
Flag Zulu (Z)
Divided into four triangles: Black top, Yellow bottom, Blue hoist, Red fly.Maritime Rule: Cargo vessels approaching berth request harbor tug assistance.