The dataset is raw diatom counts (minimum 250 count size) from a transect across a modern saltmarsh at the mouth of Dronning Marie Dal in south east Greenland (63.470N, -41.925W). The data was collected on 19/07/2014 during a research cruise to the area as part of the X_Centuries research project funded by the Danish Council for Independent Research 30 (FNU) (grant no. DFF-0602-02526B). Samples were taken from the top 1 cm of saltmarsh sediment using a knife, bagged and shipped to the laboratory where they were prepared for diatom analysis using standard methods (Palmer and Abbott 1986). Counts were taken under a light microscope at 400x magnification. Only unbroken valves were counted. The taxonomy follows Van der Werff and Huls (1958-74), Hartley (1996) and Patrick and Reimer (1966, 1975). Samples were surveyed in the field using a Sokkisha level to mean tide level, established via a pressure transducer that logged tidal variations at 15-min intervals at Timmiarmiut, 100 km to the South, during fieldwork. These tidal levels were related to tidal predictions at Tasiilaq, 300 km to the NE. This data was collected to develop a modern training set of diatom distributions across saltmarshes in Greenland to aid in reconstructing past sea-level changes from saltmarsh sediments in this area.