Abstract: An objective of the present invention is to provide a system to sense immersion of a participant into water. The system comprises a smart flag and an alarm device of a watercraft, and an FOB device of a participant. The smart flag, the alarm, and the FOB device are wirelessly connected to each other. The FOB device detects the immersion of the participant in the water. The smart flag is automatically deployed based on the detected immersion. The alarm device is automatically turned ON creating an alarm indicating an SOS signal. When the participant gets submerged in the water, the communication is ceased, thus initiating the flag to go up automatically and alarm a captain of the watercraft. Deployment of the flag lets surrounding watercraft to know that the participant is in the water.