Experiments are described that test how tide and geological structure affect saline intrusion beneath an area of coastal wetland in Hampshire, southern England. Resistivity tomography and time-dependent ground conductivity surveys were carried out at two closely located survey sites. Resultant maps and sections show clear geophysical anomalies that can be attributed to tidal saline intrusion and to the position of geological structures. Results suggest that migration of saline groundwater is, in places, out of phase with the tidal cycle, and is concentrated along sub-surface tidal channels, gravel aquifers and depressions in Chalk bedrock topography. We conclude that the seawater-fresh-water boundary in the studied wetland environment is complicated by shallow-level saline flow along geologically definable routes within the Quaternary deposits above the less permeable Chalk bedrock.