This paper examines the project planning specifications for an off-grid water desalination critical infrastructure project in Metropolitan Lagos, Nigeria taking into cognisance the State’s critical infrastructure planning limitations. Technological, financial and socio-economic data for the water desalination project were obtained and the Technology Foresight Analysis (TFA) methodology was used for analysis. The results determined a 100 million litres a day (MLD) water desalination plant design requiring an initial investment of N 70.82 billion. Estimated levelized cost of desalinated water was N 0.89 per Litre of water. With an assumed retail price of N 1.00 per Litre of water, annual revenue and profits were estimated at N 24.13 and 3.638 billion respectively. Profitability indices showed Net Present Values of N 16.15 billion, break-even time of 1 year, payback period of 13 to 20 years, and Return on Investment of 122.8% over the 25-year life span of the project. Socio-economic benefits were determined to be a regular supply of desalinated water provided at a quarter of the extant price charged by water vendors supplying the area and having a daily cost savings of N 100.56 – 201.12 million (N 36.72 – 73.42 billion annually). The study concluded that an off-grid water desalination infrastructure project for the area would be technically feasible, economically viable, and socio-economically worthwhile, and recommended same as adequate and appropriate to be deployed as a strategic municipal water supply alternative for Metropolitan Lagos, Nigeria.