Sound Case

Sound Case
What is a producer of good sound system alarm to take a boat, in case of an emergency?

As if the horn of the boat is too small … and the sound too weak. Is there something to buy, like a horn or any Whisler? Where to buy something cheap?

An air horn aerosol is a manufacturer of excellent noise backup. Walmarts has' em. A whistle will work in a pinch (like a basketball referee uses).