Abstract: Several underwater tasks require detail visualisation of a water space and bottom features. Search and identification of sea mines or explosives are good examples of such activity. To achieve high capability of detection and correct identification, high accuracy and resolution are required. One of the valuable tools, that can be used for acoustic visualisation are side scan sonars. They are in use since early beginning of underwater activity, but it is only recently that applications of high frequency, high definition sonars are being investigated. First research results show a need regarding better understanding of equipment specification. The aim of a research, reflected in this paper, is to study possibilities of detection and identification of objects located on the sea bottom or slightly buried by means of a side-scaning sonar. The sonar considered is installed on Remotely Operated cable controlled Vehicle (ROV) or Autonomous Underwater Vehicle (AUV) that introduces important limitations to size, weight and power consumption of sonar system. Theoretical evaluation of sonar parameters and definition of information needed for detection and recognition of selected types of object are required for this purpose. For experimental evaluation of theoretical consideration typical industrial equipment has been selected. Tritech International Sea King Side Scan Sonar provides basic facilities. It is modified to allow direct comparison of two images obtained simultaneously from two transducers working at different frequencies.