Remember that scene near the end of the movie Titanic where poor Jack (Leonardo DiCaprio) had frozen to death and been sent to Davy Jones Locker and Rose (Kate Winslet) was barely alive and clinging onto a door from the wreck to keep her afloat?
The rescue boat came and didn’t look like finding her until she reached for a whistle attached to the frozen corpse of a nearby sailor and blew it to draw their attention. Remember? It was the whistle that saved her.
Today, most life jackets come with a whistle attached. Some are pretty good – others are a bit pathetic and their sound simply won’t carry over distance or the noise of crashing waves and howling wind.