Sometimes, to be rescued you have to be heard. The Storm is the loudest whistle we carry. The unique patented asymmetrical shape is designed to augment and amplify sound like no other whistle. The Storm even works underwater; its sound can be heard up to 50 feet away! The Storm's focused 3150 Hertz frequency is the most readily heard tone above other noises in the environment. A whistle is vital for signalling above the sound of surf and whitewater. Remember, in most on-the-water situations a sounding device like a whistle is required by the Coast Guard. We recommend against attaching the whistle to the zipper pull on your life jacket. That can result in accidental unzipping.