The use of a proper leak detection system in pipelines is of crucial importance in water transmission systems. In these methods, we should consider the time and accuracy of leak detecting procedure for preventing energy loss and reducing environmental impacts. In these days, seawater transmission lines are used for cooling systems, and for injecting water into the oil wells to improve oil recovery. Due to the more environmental impacts of saltwater, the leak detection system must have appropriate accuracy and speed in leak detection. The purpose of this paper is to choose a leak detection system for a saltwater transmission line. First of all, the specifications of different leak detection systems are provided. Finally, according to the mentioned project conditions, the most suitable method-fiber optic system-is recommended for these conditions. The most important advantages of this system are high accuracy, rapid leak detecting, and the ability of online monitoring of other parameters, such as temperature distribution or detecting intrusion into the buried line areas. These abilities result in improving safety and optimizing operating costs.