Underwater tracking system

A positioning system for underwater communications, the system comprising

• an underwater device comprising an ultrasonic transceiver configured to receive and transmit ultrasonic signals;
• at least one floating unit configured to float on the surface of water;
• wherein a first floating unit is configured to
• obtain at least one of location information and other information based on at least one ultrasonic signal transmitted between the first floating unit and the underwater device;
• and
• based on the obtaining, provide the at least one of the location information and other information to the underwater device by transmitting, from the first floating unit to the underwater device, sequential underwater ultrasonic ping signals such that time differences between the sequential underwater ultrasonic ping signals indicate the provided information.

A surface unit for a positioning system, the surface unit comprising a first floating unit configured to float on the surface of water;

• wherein the first floating unit comprises an ultrasonic transmitter configured to transmit a first underwater ultrasonic ping signal;
• wherein the first floating unit is configured to
• obtain at least one of location information and other information based on at least one ultrasonic signal transmitted between the first floating unit and an underwater device;
• and
• based on the obtaining, provide the at least one of the location information and other information to the underwater device by transmitting, from the first floating unit to the underwater device, sequential underwater ultrasonic ping signals such that time differences between the sequential underwater ultrasonic ping signals indicate the provided information.