This dataset comprises measurements of particle size distribution, peak shear strength, residual shear strength and compressibility from two salt marshes in the UK. It also provides information on the angle of internal friction and the strength attributed to cohesion at each measurement location. The salt marshes chosen were Warton marsh, North West England and Tillingham Marsh, South East England. Undisturbed samples were taken for the shear box, ring shear and oedometer tests. Three sampling sites at each marsh were chosen for undisturbed samples: tidal flat (0-30 cm depth below the surface), marsh edge (0-30 cm and 30-60 cm depth below the surface). Bulk samples were taken from four sites within the marsh: the tidal flat, marsh edge, creek edge and inner marsh. Bulk samples were taken for root mass and particle size analysis at 0-10 cm, 10-20 cm and 20-30 cm at each of these locations, with additional samples at 30-40 cm, 40-50 cm and 50-60 cm at the marsh edge location. Field sampling and measurements were undertaken on 17th-19th July 2017 and 28th September-1st October 2017 at Tillingham and 6th-10th July 2018 at Warton.