Abstract: The aim of the paper is to present results of experimental investigation using parametric echosounder in natural conditions for profiling the sub-bottom sediments in the Gdansk Bay. The special experimental setup has been arranged allowing penetration of bottom sediments as well as precise positioning and following a given route. Measurements were conducted exactly along given routes, for those geological profiles have bean taken by means of another method. It allow as to compare detailed date obtained by means of parametric echosounding to ones given at geological map. In all investigations the primary frequency of the array was of 100 kHz, whereas the secondary frequency changed in range 5 kHz - 15 kHz.