Whistles for scuba diving

The Storm Whistle claims to be the world's loudest whistle.

According to Howard Wright, the whistle's inventor, the whistle is audible from a distance of greater than a 1/4 of a mile through trees and more than a 1/2 mile over water. Moreover, the whistle is even audible underwater!

Since the whistle works underwater, numerous Special Forces and rescue operations use it. The waterproof whistle costs about $5 or $6 and is available at a variety of department and outdoor stores. I've never used one, but it sounds like a Storm Whistle is one of the wisest investments a smart diver can make.

Source: www.divester.com