Double Dragon Neon

You'll get this fighting the giant plant boss. The boss has two arms with a bulb at the end of each. Hitting these bulbs several times will cause them to burst open exposing a monster head beneath. One of these monsters is a shark (hence the name of the cheevo). The description is a little misleading, you don't have to open both bulbs at exactly the same time (i.e., with a single hit). Simply focus on one until it opens, then open the other. The cheevo will pop as soon as you open the second bulb.