Data presented here were collected between January 2019 to December 2019 within the research unit DynaCom (Spatial community ecology in highly dynamic landscapes: From island biogeography to metaecosystems, https://uol.de/dynacom/ ) of the Universities of Oldenburg, Göttingen, and Münster, the iDiv Leipzig and the Nationalpark Niedersächsisches Wattenmeer. Experimental islands and saltmarsh enclosed plots were created in the back barrier tidal flat and in the saltmarsh zone of the island of Spiekeroog.To measure groundwater level at different elevation levels pressure loggers were deployed in dip wells within the experimental islands as well as in the saltmarsh enclosed plots. Data was measured using Hobo U20L Water Level Loggers (Onset Computer Corporation, Bourne, MA/USA) as well as a DEFI-D Miniature Pressure Recorder (JFE Advantech Co., Ltd., Tokyo; DEFI-D). The Pressure loggers were pre-calibrated by the manufacturer. Recorded data were internal logged till readout afield with the Hobo Underwater Shuttle (U-DTW-1) and following with the HOBOware Pro (V3.7.4) software or rather with the DEFI Series software (V1.02). Processing was done using MATLAB (R2018a). For depth calculations pressure data were manually corrected by atmospheric pressure.Data handling was performed according to Zielinski et al. (2018): Post-processing of collected data was done using MATLAB (R2018a).