Bluetooth (BT) is a standard for communication between devices, and can be used to send audio from a source (like an iPhone) to a receiver (like BT headphones). All BT devices use 2.4GHz radio frequency—which does not work well in water. This is due to laws of physics, as water molecules attenuate the signal. When any Bluetooth device is put underwater, the range is just few inches. Also, Bluetooth is a low-power system and the range in air is about 30ft/10m.