The development and use of unmanned undersea military vehicles is not only very challenging, but has led to serious concerns and many controversial issues in the field of international law of the sea. Ability to use these devices in various military dimensions, including; in the field of environmental recognition, underwater inspection and inspection, anti-mine operations and other military operations, their existence has become very important. However, the legitimacy of their use in the maritime arena is still disputed, and it is very difficult to determine the legal status of their use in different maritime domains. At the same time, it seems that the rules of international law in question have gaps in this regard, and do not meet the growing development of unmanned undersea military vehicles. This will certainly lead to a backlash from many governments, especially those without such technology. The present article tries to legitimize the legitimacy of the use of these types of tools in terms of legal and practical procedures regarding the use of these devices, as well as using the rules and regulations of international law of the sea and interpretation of the mentioned legal rules, trying to prove legitimacy of view of international law of the sea. Finally and, by examining the 1982 law of the sea Convention, determines the status of undersea submarines and unmanned undersea military Vehicles in certain maritime areas.