A maroon is a type of rocket

Rocket

A rocket is a missile, spacecraft, aircraft or other vehicle which obtains thrust from a rocket engine. In all rockets, the exhaust is formed entirely from propellants carried within the rocket before use. Rocket engines work by action and reaction...

 which makes a loud banging report (noise) and a bright flash. It is used as an alarm or warning, for example the British

United Kingdom

The United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...

 Royal National Lifeboat Institution

Royal National Lifeboat Institution

The Royal National Lifeboat Institution is a charity that saves lives at sea around the coasts of Great Britain, Ireland, the Channel Islands and the Isle of Man, as well as on selected inland waterways....

 uses these rockets to call the crew when the lifeboat

Lifeboat (rescue)

A rescue lifeboat is a boat rescue craft which is used to attend a vessel in distress, or its survivors, to rescue crewmen and passengers. It can be hand pulled, sail powered or powered by an engine...

needs to be launched.

The RNLI's use of this warning device was immortalized in the British folk song, "The Mary Stanford of Rye":
"On November 15th, with the storm at its height,
The Alice of Rigga was losing her fight,
Seven miles from Dungeness, she was drifting and lost,
And the crew prayed and cried to the moon,
And that's when they heard the maroon."