Подводная навигация - нужны мнения дайверов
Underwater acoustic communication
Acoustic underwater telephony is a method for underwater communication, especially with submarines. It is also known by its original code name Gertrude.
The range is very limited and depends on the water depth and temperature. Gertrude does not work through the thermocline. Simply put Gertrude is a powerful speaker that emits sound waves directly into the surrounding water. The passive sonar sensors of another boat or ship can absorb these waves.
