[en] Highlights: • Construction of the autonomous station for artificial gamma activity detection. • Submersible NaI(Tl) probe was proposed for surface water monitoring. • Testing of detection capabilities for unfavourable condition in the river environment. • NASVD method was employed for detection limits lowering. • Device fulfils legal requirement for accidental monitoring. - Abstract: This paper reports on the structure of the autonomous station for monitoring artificial gamma activity in surface water bodies for the purposes of emergency preparedness of the Czech Republic. A simple design based on the NaI(Tl) submersible detector powered by a combined solar and wind source has been employed. Data transfer is provided by a satellite connection. The detection capabilities of the device have been tested for various unfavourable conditions, and the detection limits have been lowered by using the noise adjustment singular value decomposition (NASVD) method. The detection capabilities of the device fulfil the legal requirements for emergency monitoring, and are almost equal to the detection capabilities of other available devices with a more complicated and less versatile structure.