Abstract: The underwater acoustical channel is time-variant, and even on small time scales there is often existing no ‘acoustical frozen ocean’. Popular is the use of WSSUS-channel transmis-sion modeling (Wide-Sense Stationary Uncorrelated Scattering) for the stochastic description of bandpass signals in GSM mobile phones with moving participants; since this results in a halved number of model parameters. For underwater sound applications such as detection, navigation and communication this approach provides limited a-priori-knowledge for adaptive algorithms with moving cooperative participants. The FWG of the WTD71 is collecting phase-accurate channel measurements from different sea areas in different time and application scenarios, with moving and stationary communication nodes since 2001. This paper presents a SIMO experi-ment from 2010, with a high precision continuous observation period of eleven hours using two stationary bottom nodes, mostly uncoupled from the influence of surface waves and from the sea floor. Transmitter and receiver node with a distance of two nautical miles between them were stationary installed on the bottom in shallow waters in the Bornholm Basin of the Baltic Sea. The sound speed has been measured continuously in the water column with a moving measurement chain. The question for this experiment was: Is the WSSUS-property fulfilled in water, when participants communicate motionless with negligible current, bottom influence and movements of the surface? The answer is: No, not in this experiment.