I don't know how to use the jump attack in Jaws Unleashed While holding the victim to do the stealth attack...but how?

If you like to do the jump attack, (for practice) go to the nearest beach in Amity Island and go near the swimming humans. Go under the water and take a look up on one human that you want to Attack. Press left shift while holding the swimming button ''W''. And you will take the victim faster press the bite button and you are done!