Concrete mix in Hessian bags is sometimes used to build massive slabs or walls at the bottom of reservoirs by divers and to fill prefabricated structures with concrete. (made of thick fabric impregnated with bitumen). The bags are partially filled with fresh mixture and lowered under water to the place of installation.

A more complex way is to use two coatings (usually of nylon fabric), connected along regularly spaced bands. Air is evacuated from between the fabric layers and in this state they are placed on the bottom. Then a mortar containing sand and cement in ratio is pumped between the coatings 2:1. This creates a kind of mat on the bottom, adapted to the shape of its surface. The thickness and weight of the mat per unit area can be varied by varying the length and joint spacing of the coatings. Mats covering this bottom effectively protect it against blurring.