Abstract: Background　Current emergency medical rescue training for Water system disasters on hospital ships prioritizes clinical skills over decision-making and coordination. Existing tabletop exercises primarily focus on land-based scenarios, lacking standardized protocols adapted for offshore operations. Objective　To develop a tabletop exercise plan for hospital ships during Water system disasters based on the "scenario-task-capability" framework and validate its effectiveness. Methods　An exploratory case study design was used. Based on the actual rescue mission of the USNS Comfort to Haiti, a three-phase exercise plan (emergency preparedness, response and management, and recovery and reconstruction) was developed and revised via expert panel meetings. Fifty-four trainees participated in the preliminary exercise. The Simulation Design Scale (SDS), Educational Practices in Simulation Scale (EPSS), a competency self-assessment scale, and an open-ended questionnaire were used for evaluation. Results　 A comprehensive exercise plan integrating the three-phase process with supporting tools (e.g., layout diagrams and injury cards) was developed. Ten experts (authority coefficient: 0.89 - 0.90) incorporated nine revision suggestions, confirming the protocol's scientific rigor and feasibility. Initial application showed high trainee satisfaction across all SDS and EPSS dimensions (scores＞4.7). Postexercise self-assessment scores for six core competencies—emergency preparedness, command and coordination, casualty reception, en route care, medical treatment, and logistical support—significantly increased (P＜0.01). Five optimization themes were identified from open-ended feedback. Conclusion　The developed tabletop exercise plan effectively enhances trainees' comprehensive rescue capabilities and is applicable to hospital ship emergency medical rescue training.