A system for monitoring marine vessels using a satellite network may include a plurality of satellite payloads to be carried by respective satellites. Each satellite payload may include a communications interface configured to communicate via the satellite network, a radio frequency (RF) transceiver configured to communicate with the plurality of marine vessels, and a controller cooperating with the communications interface and the RF transceiver. The controller may obtain automatic identification system (AIS) data including vessel position and call sign information via the transceiver, and communicate the AIS system data via the communications interface. The system may further include a terrestrial station configured to receive the AIS system data and determine therefrom a rendezvous between marine vessels which pass within a threshold distance for greater than a threshold time.