Department of Defense purchased 84,450 packets at a cost of approximately 

 $345,000. In addition, each packet comes boxed in a cardboard container 

 that bears a two-year expiration date, which probably accounts for the 

 continuing purchase of 15,000 to 20,000 packets per year. (This information 

 obtained from Naval Air Systems Command Code 531 as supplied by Defense 

 General Supply Center, Richmond, Va.) 



Although an effective substitute for Shark Chaser is clearly needed, 

 it is questionable whether any chemical deterrent which diffuses to form a 

 cloud around the user is practical. The quantity of material required to 

 maintain an effective concentration for the desired period of time and 

 the problem of insuring complete envelopment are among the reasons why such 

 chemical deterrents appear to offer little promise (Baldridge, 1969a and b) . 



However, the recent discovery of a biological substance that has a 

 unique deterring effect of sharks requires further investigation. A flat- 

 fish, Pardachirus , which occurs in the Red Sea and Indian Ocean, secretes 

 a milky substance that at certain levels of dilution, is highly toxic to 

 a number of forms of life and extremely aversive to sharks. It has been 

 demonstrated that a shark will not close its jaws on the living fish and 

 that under experimental conditions the substance affords protection to 

 other kinds of fish that the shark would otherwise eat. The substance 

 acts with remarkable rapidity; even fish enveloped by a shark's open jaws 

 have later shown no scratch or mark (Clark and Chao, 1972; Clark, 1974). 



3) Physical Deterrents 



Protective devices may be either active or passive. Of passive devices 

 for individual protection in a sea survival situation, one promising device, 

 the Shark Screen, appears to be an inexpensive, practical, and highly 

 effective means of preventing shark bite (Johnson, 1968). Shark Screen is 

 a bag of thin, tough plastic with a collar consisting of three inflatable 

 rings. The user partially inflates one of the rings by mouth and gets into 

 the bag. He then fills it with water by dipping the edge so that it be- 

 comes turgid, presenting to any shark a large, solid-looking black object. 

 The rings can be fully inflated at leisure. The bag retains any fluids 

 or wastes which might attract and arouse a shark. It also effectively 

 attenuates the bioelectric and galvanic fields produced by the person and his 

 gear, which otherwise might elicit attack through the shark's acute electric 

 sense (Kalmijn, 1971). It is believed that minor packaging and material 

 problems can be solved so that the final product will occupy no more space 

 than that now required for a packet of Shark Chaser. 



A new material called "KEVLAR" developed by Dupont is being used for 

 bullet-proof vests and jackets. Preliminary tests indicate that it offers 

 promise as a sharkbite resistant material which could be incorporated into 

 wet suits. 



A variety of devices for actively deterring sharks have been developed 

 or proposed, most of them for use by a diver (as opposed to devices for area 

 protection). In assessing these a number of factors must be taken into 

 consideration, including practicality, cost, reliability, effectiveness, 

 and safety for the user. A device practical for sport divers might be 

 prohibitively burdensome for UDT/SEAL personnel. Cost, within reasonable 

 limits, must be balanced against portability, effectiveness, and reliability. 



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