THE NAVY OCEAN SCIENCE PROGRAM 



43 



An experimenter afloat in a plastic bag exposes himself to potential shark 

 attack. The bag and flotation rings fold into a small package that can be attached 

 to a pilot's life jacket. 



UNDERWATER SOUND 



Within the body of the ocean, sound becomes the only practical 

 means for sensing or transmitting information beyond a few 

 feet. Fortunately, sound travels at reasonably high speed (about 

 5000 feet per second) in water, and the attenuation is not pro- 

 hibitively great. As a result, most submarine-detection systems, 

 underwater-communication systems, echo sounders, object- 

 location devices, and underwater-guidance systems are acoustic 

 devices. The credibility of our readiness for defense against 

 enemy submarines as well as the operation of our own undersea 

 fleet is absolutely dependent upon making the best use of a 

 sensing mechanism with which the environment seems to 

 conspire to make intractable. The dependence of this important 



