A vast amount of natural gas pipelines are installed underwater and they can be punctured because of various reasons such as corrosion and their increasing ages. In this study, nature of acoustic signals which are generated by leak holes on underwater natural gas pipelines is examined and a novel passive acoustic based system is proposed to detect the acoustic signals, to locate leak hole and to determine size of the leak hole remotely. Performance of the method which is based on calculating source strength is analyzed by numerical works. Parameters which are used in the numerical studies are taken from a considered pipeline. Numerical results show that leakages can be located with low average position errors far from several kilometers depending on underwater ambient noise, detection method and source strength.