A water and/or oil-impermeable sealing mat for use as a water and/or oil barrier consisting essentially of, in order, a substrate layer, a layer of swellable clay, and a cover layer, wherein
- (a) at least one of the substrate and the cover layer consist of a non-woven textile material,
- (b) all three layers are bonded together by needling,
- (c) the swellable clay is at least partially embedded in a non-woven textile layer and
- (d) the thickness of the swellable clay is less than or substantially equal to the thickness of the non-woven textile layer or layers as a whole.