Contains a chemical and a thick black dye that repels and disorients sharks. When tested by the US Navy in 1967, this product was the only one of those tested to be successful. When the foil package is squeezed in water, the crystalline acetate produces a dense black cloud. The inner bag has an attachment cord so it can be kept close to the body. NATO approved. May also be used in life rafts or airborne survival packs. Weight: 4 oz.