The most expensive thing you will ever own is the thing you spend money on that doesn't do what you want it to do. There is no good device that works above and below. There are two different devices.
A bud of mine Dave Hancock is the inventor of the
Dive Alert. I ran into him back in my manufactuing days when I had the Scuba Tool invention and he had the
Dive Alert. We used to go do all the trade shows together. The
Dive Alert is basically a scuba tank powered high pitch air horn. Carries very well over water. But underwater, it simply lets out bubbles....
I told him to come up with something that would work underwater.... and lo and behold, he found the
Hammerhead. It was not his invention, there was a company in Australia making them, and he became the exclusive US importer of them.
The unit works much like a tiny air jack - when the button is depressed, a tiny plastic piston slides up and smacks a piece of metal. Upon reaching the end, it covers up the air hole that forced it in that direction, and opens one that throws it back. This happens very fast, and results in a duck quacking type sound. It does make sound above water... but no louder that what you could accomplish shouting... it is not a great device for signaling at the surface if the boat is too far away to shout at... it's an underwater device.
Just like my Scuba Tool, even though patented, was knocked off by cheap overseas copies - the same thing happened to his Dive Alert and the Hammerhead. The Scub-Alert is nothing more than a bad copy of a Hammerhead. The hammerhead is much better quality, and I like the way it attaches much better as the fittings are at one end of the barrel, instead of in the middle, which makes it easier to point underwater without hitting the inflator hose.
The is very little if any price difference - but the hammerhead is a far superior product in my opinion.
But don't think a scub alert or a Hammerhead will be as loud at the surface as a Dive Alert... 2 different products with 2 different applications.
Just like storm whistles say they work underwater... uh... no. If you want an underwater noise maker, get a Hammerhead. If you want a surface signaling noise maker, get a dive alert.
