The hydrophone string BHC5 is used to receive P-waves in water filled boreholes. This receiver is used for P-wave tomography is a standard method for high-resolution geological structure exploration between boreholes. P-waves are generated in one borehole and being transmitted to the other. P-wave tomography measurements are easy to analyze due to the easy recognition of the first arriving seismic waves.The BHC5 reciever consists cable drum, hydrophones moulded on cable and battery box for pre-amplication. Accessories, such as a cable spooler device for cable on drums and a clamping device supports a proper positioning and clamping the cable during operation.