Naval operations in coastal waters are challenging the modelling support in several disciplines. An important instrument for undersea defence in the littoral is the LFAS sonar. To adapt to the local acoustic environment, LFAS sonars can adjust their operation depth to increase the coverage of the sonar. The optimal depth can be determined by a reliable sonar performance model. In 2003, during a sea trial in the Mediterranean Sea, a series of experiments was conducted to verify the sonar performance modelling for several target and sonar depths. For these experiments, the propagation situation was understood, and target echo level and sound propagation loss was favourably compared with the modelling.