Specifically designed for HR borehole surveys Fast and simple infield operations High sensitive acceleration-free piezoceramic sensors Small diameter and light weight Compatible with any seismograph WellStreamer is a borehole hydrophone array, specially developed for seismic acquisitions in water-filled wells. We designed an exceptionally easy to use and robust receiver tool with sensitive acceleration-free piezoceramic sensors and signal preamplifiers in each module for registering compressional (P) waves during VSP, cross hole surveys, parallel seismic testing, and other high-resolution borehole seismic techniques. WellStreamer is also used for geotechnical monitoring of the structure of berths, dams, and other hydraulic structures - in this case, it can be located below the water surface on one side of the construction. Measuring the length of piles by parallel seismic testing, geotechnical control of the soil stabilization process, control of the continuity and thickness of the ice wall during the mine shaft construction are also hydrophone array applications.