Submarines can't normally communicate directly with anything above the water due to the physical limits of their signal, but that might change in the near future. Researchers have developed a wireless system that can transmit data from an underwater source to the air. The approach, known as translational acoustic-RF communication (TARF), sends a sonar signal to the surface, where tiny vibrations at different frequencies correspond to the 0s and 1s of binary data. Above the water, an extremely high frequency radar (30GHz to 300GHz) can pick up on minuscule changes in signal angles that relate to the data bits. It's just a matter of processing the bits into meaningful data after that.