This work experimentally examines the influence of integrating a floating sponge layer on the performance of a solar still distillation unit (SSDU). Several densities (16 to 35 kg/m3) and thicknesses (0 to 40 mm) of the sponge are tested at different depths (10 to 40 mm) of saline water in the SSDU basin. The results report that integrating the sponge in the SSDU changes its operational principles, temperatures profiles, and performance. Besides, integrating a sponge of 16 kg/m3 density supplies freshwater productivity and thermal efficiency higher than that of the conventional unit, and their increases are reduced by increasing the sponge density. Moreover, these productivity and efficiency are augmented by increasing the sponge thickness from 10 to 30 mm and then decrease at 40 mm sponge thickness, and they are also reduced by increasing the saltwater depth in the basin. Finally, the maximum daily freshwater yield and thermal efficiency are recorded as 4.9 L/m2.day and 37%, respectively, by applying a sponge of 16 kg/m3 density and 30 mm thickness at 10 mm saline water depth, with corresponding increases of 58.1% and 55.3%, respectively. Besides, the cost of one-liter freshwater is reduced by 35% compared to that of the conventional unit.