A sliding subsea foundation comprises a polymeric shoe layer on the underside of a mudmat or subsea structure. The shoe layer defines a soil-engaging face that comprises an array of parallel grooves. The grooves are shallower than the thickness of the shoe layer such that each groove has a closed top, defined by and integral with the shoe layer, that spans the groove. Where a subsea structure is supported on the foundation with a subsea pipeline attached to the structure, the grooves are substantially parallel to a longitudinal axis of the pipeline.