Developing technologies that can supply water and energy in a sustainable manner is essential in addressing resource scarcity of small communities. The main motivation of this article is to find, through the analysis of different study cases, the optimal design of an Open-Cycle, Ocean Thermal Energy Conversion (OC-OTEC) system. Specifically, we propose optimization formulations to determine the operation policy and sizing of the system while considering four conflicting objectives: minimizing the total annual cost, minimizing CO emissions, and maximizing the generation potential of the products derived from the operation of the OC-OTEC (water and energy). The formulation captures seasonal effects and restrictions on water and energy demands determined by the end-user as well as diverse technical, operational, and design restrictions. The proposed model is applied to a study area in the Pacific region of Mexico.