TANK BANGER

The Scuba Tank Banger is a simple underwater signalling device built from corrosion-free plastic and a length of surgical or elastic rubber tubing, worn stretched around the base of a scuba cylinder. To get a buddy's attention, the diver pulls the attached ball or knob away from the tank and releases it, producing a distinct clanking sound that carries well underwater. The device works passively while diving and requires no maintenance beyond a rinse after use.

Its main advantage is directness: unlike a shaker or air horn, a tank banger stays fixed to the cylinder, keeping a BCD uncluttered and putting the noisemaker within easy reach without needing to locate a separate accessory. It's audible to buddies at moderate range underwater, though exact distance varies by model, tank material, and water conditions. The elastic strap is designed to stretch over a range of cylinder sizes and can be fitted for either left- or right-handed operation, and most versions can be used by either pulling for a loud signal or lightly tapping the ball against the tank for a quieter one.