Ships are the most important means of transportation for maintaining the marine economy in most countries. Coastal patrol is an important task of the state to prevent smuggling and other dangerous coastal activities. However, unfortunate accidents involving people on board ships and coast guards drowning in the sea occur from time to time. To save the lives of those who have fallen into the sea, most international searches are carried out by satellite searches, helicopter rescue, and the dispatch of boats. They are not only time-consuming but also inefficient. For this reason, we propose in this paper a real-time alarm, dynamic global positioning system (GPS) tracking, and monitoring system for man overboard (MOB). The system consists of four parts: wearable sensing aids, modular long-range access points (LoRa APs), physical electric fences, and a central control system, as well as three methods of detecting and protecting against MOB. These methods include real-time notification of MOB with wearable sensing aids, virtual electric fence monitoring based on the size of the ship, and instant notification triggered by a physical electric fence around the ship. As shown in a laboratory test and an actual sea test, the three MOB sensing methods developed in this research can perform instant detection and notification actions. We have thus demonstrated a method for the real-time detection of MOB by a shipwrecked ship itself that also promptly proposes a rescue action.