Radio signals can not be transmitted underwater. Radio signals are electromagnetic waves and therefore attenuate (die) as the water grounds the signal instantly.
The Scubaphone Sport therefore sends the signal through a transducer (a piezzo-electric ceramic) that converts the signal to an ultrasound signal. Water is an excellent conductor of sound. In fact sound in water travels at 4^1/2 to 5 times the speed of sound in air, approx. 1500 metres per second. The ultrasound signals travel omnidirectionally from the transducer mounted on top of the divers head. The signal travels essentially in line-of sight, but echo bouncing is effective. The divers suit and gear will absorb the signal. That is why the top-of-the-head-mount of the transducer permits the widest possible transmission with minimum body shadowing.

Up to 500 feet, depending on water conditions. Usually divers are very close to each other and it is recommended that divers still dive in Buddy pairs and remain close to each other. If your Buddy calls for help you should be close by to assist. A surface unit is available that permits the Dive Master to control the divers and monitor the dive and take control in emergencies.

The battery consists of four AA cells. This is the most commonly available battery in the world and it is also the most inexpensive battery. The Scubaphone Sport is equipped with sophisticated software, including a smart power management system, that conserves battery power by turning itself off when you exit the water and by being in low power mode until you speak(commonly referred to as Vox for voice activated transmission). As a result the battery will last four hours of diving at fifteen percent communication, about as much as most divers will talk. Never throw expended batteries in the ocean. Heavy metals in batteries are deleterious to the environment. We recommend you use rechargeable batteries. They are cheaper over time and because they do not get thrown in the ocean are easier on the environment.