If it is the same manual I was issued in 1991, I got a kick on the Army's idea of dangerous sharks. I do not remember where it is listed, or the exact quote. It stated that Dangerous Sharks have big mouths, with big teeth, non dangerous sharks have small mouths and small teeth. Sounds logical I just found it on line, not exactly the same, but humorous non the same.
Shark
Sharks are the most feared animal in the sea. Usually, shark attacks cannot be avoided and
are considered accidents. You, as a survivor, should take every precaution to avoid any
contact with sharks. There are many shark species, but in general, dangerous sharks have
wide mouths and visible teeth, while relatively harmless ones have small mouths on the
underside of their heads. However, any shark can inflict painful and often fatal injuries,
either through bites or through abrasions from their rough skin.