Like Navigation the key to modern communication is a hub, and the hub is the Multi function display (MFD) and to a degree also secondary displays such as the Raymarine i70 Of course the main source of communication is the Radio (VHF).
Additionally non verbal communication is now becoming more important in our crowded waters which comes in the form of Automated Identification systems (AIS). All commercial vessels and boats over 50mtrs are now required to transmit their location speed direction of travel and their identity such as the MMSI code. This is a system adopted from the aerospace sector where aircraft “squawk” this information using Interrogation friend or foe (IFF) aircraft information is overlaid onto a RADAR scope for Air-traffic to see.
Likewise AIS can do the same thing with an MFD AIS information can be overlaid onto a chart or RADAR image and now can also be used with Augmented Reality (AR). Small vessels at the moment are not required to transmit AIS data but this could become a future requirement.
AIS data can be received by some VHF units like the Raymarine Ray70/73 and shared on the NMEA Network to be seen like a RADAR image on a suitable MFD or secondary instrument. This won’t totally replace RADAR but is a good option to consider. Small vessels can transmit AIS data with the use of a class B transponder meaning you will certainly be seen by larger vessels and replaces the mast fitted RADAR reflector. Another great communication source of course is the internet and nowadays you can receive data from a mobile network up to around 12 miles off shore using a 4g network it is now becoming common to have a 4g router with a SIM card fitted on board a boat giving access to email voice calling FaceTime and internet TV including Netflix.