Results are shown from trials with a neutrally buoyant underwater buoy performed in a Norwegian fjord in collaboration with Norway and Canada. The buoy was floating at the interface between the fresh water above and the heavier salt water below and was equipped with electric and magnetic sensors. The background noise level was low except at the eigenfrequency of the buoy at around 0.2 Hz. Strong surface waves could set it in motion. The magnetometer was used to monitor the movements and the orientation of the buoy. A source was pulled after a boat to measure the electromagnetic wave propagation in the fjord. A comparison between a Swedish sensor system with carbon fibre sensors and a corresponding Canadian system with silver/silverchloride sensors led to the conclusion that the two systems had no significant difference in function and sensitivity. - P