Flood dykes surrounding the upper Bay of Fundy (BoF) are facing increasing risk from rising sea levels and storm surges. As plans evolve to mitigate these risks, largely by raising existing dykes, it is relevant to consider approaches that may be used to efficiently screen for any weaknesses in them and their foundations. This study aims to examine whether geoelectrical surveys could provide a relatively rapid screening method, helpful for developing a more targeted and more detailed geotechnical investigations. Such methods have proven useful in other jurisdictions (Europe, Japan, USA) but have not been considered in a megatidal coastal environment like the BoF. The study has two main questions: (1) Can geoelectrical surveying identify internal vulnerabilities in an earthen flood dyke? and (2) How do large tidal fluctuations affect the resulting geoelectrical models? Field surveys in the Shepody dykelands (SE New Brunswick) employed electromagnetic conductivity mapping (EM) and electrical resistivity imaging (ERI). Both methods show that the dykes are generally resistive with rare conductive zones. The most prominent conductive anomaly extends into the foundation sediments. Targeted soil sampling and laboratory testing indicate that high conductivity is strongly correlated to elevated saline water content, interpreted to be indicative of enhanced saltwater intrusion in the foundation and increased seepage into the dyke during high tides—both of which can affect the dyke’s stability. To evaluate tidal effects, 3D time-lapse ERI was conducted over the anomalous segment. The maximum resistivity change observed was about a 15% decrease at peak high tide. Overall, the 3D results are consistent with the 2D interpretation, indicating that tidal fluctuations have a measurable but limited impact on the resistivity models.