This report presents the analysis of electromagnetic data recorded at a sea trial in the Baltic Sea, in the fall of 1999. The analysis can be categorized in two sections, a comprehensive background study and a brief signal detection study. The background study is done by means of time-frequency analysis and statistical tests of the data. The time-frequency analysis shows that the two measuring units used in this study have quite different characteristics, due to the data acquisition system. From the statistical tests we find that the background is stationary and linear for all the sensors. It can not be determined if the background is gaussian with the gaussianity test. The detection study indicates proper functionality of the energy detector, but the overall detection performance is quite low. However, the results should be considered as a lower bound for the system. Finally, a few suggestions for modifications that could improve the performance are given.