Sealing compounds, permanently plastic, for waterproofing underground holes necessary for the crossing of wall structures, by one or more cables and/or pipes. They do not harden over time, unlike silicone-based products, and thus make it possible to replace and/or remove cables, optical fibres, pipes, without damage to the sealing. They can be applied in damp environments and even in the presence of running water. They do not alter their characteristics over time.