Marine Insight - There are different types of signals one can use onboard ships to indicate that your ship is in distress. Let us know in the comments what other distress signals
Navigation markers, sounds, lights and flags
Examples of Sound Signals Used for Encountering Situations
What do six short blasts and one long blast mean from a ship horn? - Quora
Oregon State Marine Board : Sound Producing Devices : Boater Info : State of Oregon
What Do Cruise Ship Horn Signal Blasts Mean?
FAQ] What are the Different Types of Alarms on Ships? - mfame.guru
Light, shape and sound signals – Maritime Progress
COLREG
eOceanic
An Easy Guide to Whistle Signals: What They Mean, How to Respond