RESUMEN
BACKGROUND: In Brazil, the Mobile Emergency Medical Service (SAMU) is a model of mobile assistance and care for emergencies standardized throughout the country. The water ambulance service within the SAMU operates in riverside and coastal areas, and faces challenges and peculiarities that increase the complexity of providing a high-quality and safe emergency care service. OBJECTIVE: To develop organizational design guidelines aiming to improve resilient performance of complex systems, with an application to riverine and coastal mobile emergency care in Brazil. METHODS: Data collection followed an ethnographic approach. Fieldwork was carried in a participatory way, based on worksite technical description, semi-structured interviews with managers and emergency care teams' professionals, and work observation whenever possible. Five regional SAMU coordinations were visited. Data coding employed content analysis and grouped data excerpts according to concepts of capacity and demand. Interfaces were identified between demand and capacity elements and adaptations led by system agents, orienting the proposal of guidelines for organizational design as solutions to face the verified gaps. RESULTS: Design guidelines produced spanned composition and training of both intervention teams and dispatch central teams, uniforms and personal protective equipment (PPE), decentralized water bases, means of communication, intervention protocols, biosafety and inter-sector actions. CONCLUSION: The approach enabled framing and assessment of specific design elements according to resilience engineering concepts, which in turn showed paths for improving the service and reconciling work-as-imagined and actual system functioning.