Is this a type of walking stick? Its body and legs are like a walking stick, but its front legs are like a mantis. (Hooked, jointed and serrated). Also, a strange long "tail" that's looks like a stinger. It lifts its front legs in defense (or attack) whenever you move near it. Its face and head are not shaped like a mantis though.
This is a water scorpion, a predatory aquatic insect in the family Nepidae. Yours is in the genus Ranatra, see http://greglasley.com/nonBirds/waterscorpion.html
