The study carried out an environmental assessment for two seawater reverse osmosis (RO) plants located within the Arabian Gulf considering subsurface intake alternatives and differing energy source options. The study used life cycle assessment to quantify the environmental impacts for open intake pretreatment vs. subsurface intake pretreatments of two plants with operating capacities of approximately 175,000 m3/d and 275,000 m3/d respectively. For both RO plants, electricity and chemical inputs were considered. Significant energy reductions of 30% were observed with subsurface intakes for extraction and pretreatment, resulting in a plant-wide energy saving of 6%. Open intake pretreatment had higher environmental impacts compared to subsurface intake across all impact categories, although in some impact categories significant differences existed between the two similar plants due to differences in chemicals used. The study further established that the renewable PV power generation resulted in the lowest global warming potential (GWP); however, a significant trade-off occurs with this energy source since it had the highest impact relative to both ozone and abiotic depletion potentials and was also worse than natural gas for both marine and human toxicity potentials. The GWP reductions achievable using a subsurface intake for the larger of the two plants is equivalent to 58,000 tons of CO2 per year, or more than 12,000 cars, making subsurface intakes a worthy alternative to conventional open intake systems in the Arabian Gulf region. Marine aquatic eco-toxicity potential was identified as the most significant normalized environmental impact, which should be best managed through using natural gas as an energy source.