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Saltwater and industrial contamination is gradually rendering groundwater in coastal India undrinkable, and the impact is most severely felt by the populations who lack access to centralised water treatment facilities. This paper details the design, construction, and initial performance assessment of the Umbrella Desalinator, a portable passive solar still intended to serve precisely these households. The first iteration of the prototype used a Peltier module and vacuum pump to actively cool and remove water vapour from the air. The second iteration, presented in this report, utilises solar energy for heating and does not require electricity or other consumables to operate. The device consists of a transparent canopy, mounted atop a darkened absorber sheet, which is held open by collapsible ribs. Solar radiation passes through the canopy and heats the water stored underneath, and the resulting vapour condenses on its surface and is funneled into a collection pouch. The expected daily yield under clear skies is between two and four litres of water. This paper further details the selection of components and the technical and ethical considerations surrounding the construction, as well as an appraisal of the performance of the completed prototype. Due to monsoon conditions, the performance of the prototype in Mumbai could only be partially evaluated. As such, this report reflects on the completed development process and presents an assessment of the potential utility of the design in the target environment. The findings suggest that a low-cost passive desalinator which employs an umbrella-like folding mechanism can indeed be constructed, and further testing in the target environment would be beneficial.