Markwort Storm Safety Whistle on Blister Card, Black The Storm Safety Whistle is ideal for all your favorite outdoor sports like hunting, diving, and hiking. Its larger size makes is easy to grasp and use for personal protection. Used by Police Departments, the U.S, Military, U.S. Coast Guard, and Emergency & Diving Operations who appreciate their all-weather use. Blown and heard on land, up to 1/2 mile, and even underwater, up to 50 ft. A non-corroding thermoplastic housing is easy to grasp, and the patented double chamber design allows it to be blown when held reight side up or upside down. each whistle purges moisture yet still delivers a loud, penetrating sound easily heard in any environment.