The dataset details the grain size distributions of 459 subsamples from 18 soil cores collected from across 14 UK saltmarshes between 2018 and 2021. The work was carried out under the NERC programme - Carbon Storage in Intertidal Environment (C-SIDE), NERC grant reference NE/R010846/1 Full details about this dataset can be found at https://doi.org/10.5285/aa4c9ff1-8215-49bf-b044-32e66f290d95