“…These works can be classified into two categories: software-based internal methods and hardware-based external methods [14,22]. Among them, the internal method mainly monitors related gas flow parameters, such as flow mass or volume, negative pressure waves, and gas flow rate, and then judges whether a subsea gas leak is occurring [14,19,22]. By contrast, the external method needs external sensors such as hydrophones [13,19], optoelectronic sensors [17,18], fiber-optic cables [15,16,23], and optical cameras [14,20,21,24] to realize the subsea gas leak monitoring.…”