Kestrel weather meters. Originally designed for the rowing industry, the Blue Ocean waterproof megaphone is popular amongst the U.S. coast guard, military, fire and police departments, life guards, and others who need to project volume over a group of people. This waterproof megaphone was designed to withstand severe weather, and floats if dropped in the water.
Features include: rechargeable battery, removable bumper, optimal shape, siren and horn buttons, large dial volume and power buttons for easy adjustment and control.
See more at http://blueoceanmegaphones.com