Abstract: The main goal of the paper is to present passive, autonomous system to observe objects moving on the sea surface and floating in the depth prepared to work in very shallow water. Complete system will be described starting from hardware realization finalizing on configuration of sensors and presentation of algorithms implemented in prepared to this project software ( alarm types, setting parameters responsible for alarm generation etc.). Finally example of object detection will be presented concentrating on remotely operate vehicles ROV – seabotix and combustion motorboat. At a given point of discussion, stability of algorithms eliminating the occurrence of false alarms will be presented.