The problem you've just seen a great white. You're out of air. Or perhaps you discovered a gold brick in the sand. How do you get your buddy's attention, or help from others? The solution give Reef Net's new "H2YO" a shake to emit a loud and distinctive rattle that can be heard at great distances underwater. Well maybe it's not that drastic of a problem, but you get what we mean! Maybe you just found a hole full of lobster or super macro shot you want your buddy to photograph. The Noisemaker is made from durable plastic with a large internal ball and steel split ring for attachment to gear. There are many reasons to use an H2YO instead of alternative signaling devices. It can't be forgotten on shore/boat like a tank banger since it stays on your BC. The sound pattern is unique and easily identifiable. Does not sound like a tank banger...the days of wondering "who's banging?!" are over. It doesn't require an air supply like many other noisemakers. It doubles as a gear identifier (different colors for different people) and it's virtually indestructible.