In May 2017 a dual-frequency echo sounder was used in Goose Pond at the former Callahan Mine site to obtain seismic profiles in very shallow water. The method uses two fixed transducers mounted in the same housing. One transducer was 24 kiloHertz (kHz) and the other was 200 kHz. The CSP-DSO data were collected concurrently with continuous resistivity profiling data, and the water bottom was determined with the 200 kHz transducer. The seismic traces on the low frequency transducer were used to analyze the subbottom materials. In some places the signal penetrated the subsurface, but in many places the signal reflected off of a shallow subsurface layer. The data quality was not as good as the swept frequency (chirp) CSP data, but the dual-frequency sounder could be used in much shallower water than the chirp system.