A B S T R A C TGenerally, in fatal accidents that occur at sea, the victims suddenly enter cold water. Because the victims can survive for only a brief time, the required rescue time is often more important than the quality of the victim's lifejacket or life-saving equipment. Additionally, locating a person in distress at sea during night time or inclement weather is difficult. We believe that rescue equipment such as SARTs (Search and Rescue Transponders) and EPIRBs (Emergency Position Indicating Radio Beacons) are effective rescue devices, but these devices are still expensive, large, and limited to personal use. For these reasons, establishing the proof-of-concept for a new life-saving appliance (LSA) using the characteristic radar cross-section has been proposed. To realize proof-ofconcept for this device, the service environment must be considered and the functional reliability of the LSA, based on the characteristics of the human body, must be guaranteed. In this paper, a detailed design of the LSA is proposed using a systems engineeringbased design process and quantitative functional reliability verification tool.