The JetScream Whistle focuses manmade air streams through harmonically tuned chambers to create a piercing shriek audible over most other natural and manmade noises. Due to its pea-less design, JetScream even works when wet, making it the perfect accompaniment to all outdoor activities near rivers, lakes, or oceans. Flat enough to fit in your pocket and attached to a lanyard, the JetScream is just as useful in the city as it is in the woods.