Sentence:  Each carried a shielded crimson dive light, invisible from the surface, which gave objects a gray, pallid distortion. They were also equipped with a knife strapped to one calf, a small P-6 pistol holstered on the other, a compact <WSD>butt bag</WSD> of tools, and a short bang stick armed with a twelve-gauge shotgun shell to ward off sharks. 
Meaning of the word marked with <WSD> tags:  fanny pack