Abstract: A safety mat for protection against erosion and/or undermining consisting of a number of parallel tubular members containing a filling material and being interconnected by cross-binding ribbons placed at right angles to the tubular members. As filling material is used a granulated material of an average density of at least 1.6 Kg/dm.sup.3, and the tubular members have a degree of filling of substantially 75%. Using a relatively heavy filling material that is introduced relatively loosely a mat is obtained having great flexibility, being able, therefore, to lie close up against even a domed bottom.