A mechanical water still (10) includes an impervious dome-like upper surface (12) and a membrane base (14) that is coupled (26) to the impervious dome-like structure (12) to form, when inflated, a chamber (20). The membrane base (14) supports a water pervaporation process therethrough. A water collection well (16) has an opening into which water droplets condensed from the water pervaporation process collect. The water collection well (16) is sited within the membrane base (14) and generally extends outwardly and downwardly from the membrane base (14), as shown in FIG. 1. In use, a contaminated water source (24) is brought into, ideally, complete contact with the membrane base (14), with the water collection well (16) arranged both to act as a heat sink into the water source (24) and to provide stability to the water still (10) when floating and immersed in the water source (24).