Abstract: Tough transmission properties of shallow water acoustic channels (SWAC) highly limit the use of underwater acoustic communication (UAC) systems. An adaptive matching of modulation and signaling schemes to instantaneous channel conditions is needed for reliable data communications. This creates, however, unique challenges for designers when compared to radio transmission systems. When communication system elements are in move, the accuracy of both the measurements of channel impulse responses and estimates of transmission characteristics is strongly limited, due to rapid variations of the channel performance. This paper describes communication tests of a model of the orthogonal frequency division multiplexing (OFDM) data transmission system. developed by the authors. The measurement procedures and signal processing algorithms were, first, tested in reverberant air-acoustic channels available in the laboratory, and, next, verified in natural conditions in a lake. The air acoustics trials prove to be effective and methodically correct.