Cruise ships always fly the individual flag of their nation of registration.

They also fly the flag of the place they are sailing, changing them as they arrive in a new port. They probably also fly their cruise line’s logo flag.

READ MORE: Little-known rule about alcohol on cruise ships

How cruise ships communicate

But ships also use other flags to communicate at sea.

These flags are also used as part of the International Code of Signals. And they all have different meanings.

We were shown the different flags neatly stored on a visit to the bridge on cruise ship, Crown Princess.

Marine Rescue NSW says the 26 square flags represent the letters of the alphabet. They feature five colours: red, blue, yellow, black and white.

Specific flags let other vessels know things.

For example Alpha, which is blue and white, means diver down; keep clear.

W, or Whiskey which is squares of red, white and blue, indicates required medical assistance.

A yellow flag, known as Quebec, indicates the vessel is “healthy” and requires free passage.

Flags can also be used in combinations, which means they then have other meanings.

Sometimes a whole string of the different flags are used as decoration, flying above the decks like bunting.

Sound and radio signals are also used by ships to communicate. A ships horn, for example, is one such thing and the number of blasts means different things.

Three blasts means the ship is reversing. Five means there is an emergency.

It’s also used as a fog horn when visibility is bad so other vessels know it’s there.

Another cruise ship tradition explained

Another tradition is for ships to be christened.

Maritime historian Chris Frame told 9Travel that the smashing of the Champagne on the hull is believed to have been begun by Queen Victoria, when she named naval ships.

Frame says “it’s a traditional ritual steeped in superstition from a historical perspective, that today is undertaken largely for media and public relations purposes.”

Royals and celebrities are named as ‘godparents’ with actress Hannah Waddingham TV host Drew Barrymore along recent A-listers to be given the honour.

Meanwhile, there are plenty of sailing rules passengers may not know about.

Shaking hands with the captain may seem courteous and respectful, but is banned on many vessels.

In several countries, particularly parts of Africa and the Caribbean, camouflage-patterned clothing is reserved for military personnel.

Plus many regions have strict agricultural controls to prevent the introduction of pests and diseases.

The first ship to take passengers on a cruise from Australia, rather than transporting them from one place to another, was P&O ship Strathaird.

Originally a mail ship that sailed for the first time in 1931, it was mainly used to transport ‘ten pound poms’ between England and Australia.

But on December 23, 1932, it set off Australia’s first cruise from Sydney to Brisbane and Norfolk Island with 1,100 passengers for five days.