At the semi-natural constructed Marconi salt marsh, bed level change data were collected using state-of-the-art Acoustic Surface Elevation Dynamics (A-SED) instruments. This recently developed instrument measures the distance between the bed and the instrument through the echo of an acoustic signal. The instrument is set-up to be able to collect measurements when the sensor of the instrument is fully inundated. A burst of eight samples (sampling frequency of 5 Hz) was stored at a measurement interval of 5 to 15 minutes. The instruments were installed downward looking, with the sensor head aimed vertically at the bottom. The instruments were serviced, cleaned and data were downloaded every two to three months. A post-processing script was developed in Python to convert the acoustic return signals to bed level change data. The measurements were validated with manual readings of the height above bed (HAB) of the sensors every time the instruments were serviced.