This Gardline marine geophysical survey took place during July/August 2007 in the Thames Estuary aboard the THV Alert. This survey was undertaken for the Thames Regional Environmental Characterisations Project. This study was funded by the Marine Environment Protection Fund (MEPF) a marine component of the Aggregate Levy Sustainability Fund (MALSF). Seabed samples were obtained using a clamshell grab and photo and video data exist for these sites. Sea floor data collected were high-resolution multibeam bathymetry, backscatter, magnetometer and side-scan sonar. Subsurface data were gathered using a Surface Tow Boomer. Most of the data were recorded digitally. These data are archived with the MEDIN Data Archive Centres (DACs), including the BGS DAC for geology and geophysics. Technical details for the survey are contained in Gardline Report 0871/Ops.