The estimation of water current by using acoustic Doppler current meters (ADCM) is a well-known method. Determination of the water current is based on the Doppler shift caused by the movement of small particles in the water, related to the current as an average. These movements cause a Doppler shift with an assumed Gaussian-shaped distribution in time. This assumption is valid for clean water and water where one particle size dominates the scattering and thereby the Doppler shift. If many bubble size are involved in the scattering, the Gaussian-based estimators may generate errors.