Abstract: Maritime threat-sensing buoys include sensors—such as acoustic, radio frequency, visual, or other sensing devices—that track, identify, or classify hypersonic or underwater threats in real time. Some examples of suitable sensing devices include microphones, radio-frequency (“RF”) detectors (for example, RF antennas), infrared detectors, and machine-vision detectors. The maritime threat-sensing buoys may be deployed using aerial or maritime vessels, and may host payloads, such as threat-sensing mechanisms, batteries to power the threat-sensing mechanisms, solar panels configured to deliver electricity or other energy to the batteries or other devices, and other cargo or contents.