The increasing demand for water in arid regions has driven the adoption of seawater desalination plants as critical infrastructure for industrial and domestic applications. However, these plants face unique challenges, including high operational costs, environmental vulnerabilities, and system reliability concerns. The critical nature of these infrastructures demands maintaining elevated levels of availability and demonstrating robust resilience. Resilience is framed as the system's capacity to recover from disruptions and maintain operational efficiency under varying conditions. Quantitative assessment of resilience is essential to facilitate the development and implementation of optimal strategies that ensure operational continuity. This paper puts into practice a novel approach to evaluate the resilience of a seawater intake and pumping system using permutation entropy computed using time series availability data derived from different maintenance strategies. The methodology integrates reliability block diagrams (RBD) and symbolic time series analysis to identify critical components and evaluate maintenance strategies. A case study of a seawater pumping station demonstrates the application of the proposed resilience index. The analysis explored four scenarios to evaluate how these changes improved the system's resilience: the first three hypothetical scenarios involved testing improvements in the maintainability and reliability indexes of the critical pump. These improvements matched the values of these parameters to the benchmark of the pump, historically showing the best indicators, first one by one, separately, and then both changes simultaneously. The initial resilience index was 0.652 in the baseline scenario. Scenario 1 (reduction in MTTR) showed a negligible impact, while scenario 2 (reduction in downtime) increased the resilience index to 0.682. The combination of both (scenario 3) maintained the index at 0.682, emphasizing the importance of reducing downtimes. Scenario 4, which consisted of reducing and standardizing the frequency of planned maintenance to 100 h, significantly raised the resilience index to 0.778. The results highlight how adjustments in maintenance strategies, including the reduction in preventive interventions, impact the system's resilience and availability. The study also underscores the importance of aligning maintenance strategies with resilience goals to enhance the operational reliability of marine infrastructure. By providing a quantitative tool for resilience assessment, this work contributes to the sustainable management of desalination plants and offers practical insights for engineers and decision-makers in the marine engineering and water management sectors.