This dataset provides water depths and water surface elevations collected during bathymetric surveys of the main channel of the Wax Lake Delta within the Mississippi River Delta (MRD) floodplain of coastal Louisiana, USA. The measurements were made during the Pre-Delta-X Campaign in Fall 2016. The in situ continuous (1 Hz) surveys of channel bathymetry were conducted using a SonarMite Hydrolite Single Beam Echo Sounder mounted on the side of the research boat. The sounder was located directly beneath the Septentrio global navigation satellite system (GNSS) antenna, about 30 cm below the water surface. The sounder depth observations were integrated with the GNSS location and elevation data into one data file per day for October 16-20. These bathymetry measurements were used to generate a merged digital elevation model (DEM) through interpolation with ancillary DEMs to expand the existing wetland DEM to include channels. The merged DEM product is distributed in GeoTIFF format.