“…A UWA channel may be viewed as a heavy multipath environment, since signal propagation does not take place only across the aforementioned "LOS" path but signal echoes, denoted as rays, originating from points of discontinuities in propagation speed, such as the sea-surface [22]- [24], sea-seabed [25], [26], or other under-sea objects [27], also occur. In order to compute attenuation and multipath fading, the today's UWA channel models vary from applying empirical equations [28], [29] to using more accurate simulation tools and theories [16], [17].…”