1. Scuba divers can use hand signals to communicate.
2. They can also use underwater writing slates.
3. They can use wireless and hard wired communication systems as well. A transducer on the diver's face mask will converts his or her voice into an ultrasound signal. The other diver will have an ultrasound
receiver that receives that signal and changes it back to a sound that the diver can understand.
divers’ helmets, which have built in microphones and speakers, can be also linked to
intercom stations, such as Clear-Com, on board the ship though an umbilical, enabling them to correspond with
the Dive Supervisor and the crew on the deck.
Read the full case study here: World Class Vessel Maximizes Well Intervention Collaboration