The use of unmanned naval vehicles (UNVs) is becoming increasingly widespread, especially in dangerous and labour-intensive missions. In addition to military areas such as combating maritime banditry, reconnaissance/surveillance, anti-submarine warfare and mine clearance, the main areas of use of UNVs are scientific issues including the measurement and recording of hydrographic data, meteorological support services and topographic studies for the creation of seabed maps.
There is an ongoing debate as to whether UNVs meet the definition of a ship in the United Nations Convention on the Law of the Sea (UNCLOS) and therefore fall within the scope of the articles on “harmless passage” and “freedom of navigation at sea”, and no clear consensus has been reached on the issue. However, by interpreting the relevant articles of UNCLOS, it is assessed that the UNVs can benefit from these rights if they comply with the sovereignty rights of the coastal state and the restrictions set and do not participate in military exercises.
The US unmanned underwater vehicle (UUV), which was seized by the Chinese Navy in the South China Sea in 2016, is a case in point. The US claimed that the UUV was used to measure oceanographic data such as salinity, temperature, etc., while China stated that its purpose was to collect military intelligence. 
Recently, allegations of the use of UNVs in the sabotage of the Nord Stream 1 and 2 pipelines and in the Russian-Ukrainian war have frequently appeared in open sources. Although these allegations have not been proven or acknowledged by the countries that allegedly used them, they have been followed with public interest.
On September 26 and 27, 2022, successive explosions on the Nord Stream 1 and 2 gas pipelines raised the possibility of deliberate and well-coordinated sabotage. Separate investigations by Sweden and Denmark, through whose Exclusive Economic Zones (EEZ) the pipelines pass in the Baltic Sea, and Russia and Germany, the starting and end points of the pipeline, as well as the operating company “Nord Stream AG” are ongoing, and no clear findings on how and by whom the alleged sabotage was carried out have yet been made public.
The average depth of 43 meters in the Bornholm basin, the area where gas leaks were detected on the sea surface after the explosion, is a depth suitable for the use of specially trained divers and remotely controlled vehicles, but not suitable for such an operation by nuclear submarines. However, it is believed that the placement of explosives in pipelines for sabotage using unmanned underwater vehicles is preferred because it can be done in a shorter time and is less likely to be detected.
Another development was the public reports about the explosion of bombs planted on the Kerch Bridge on October 8, 2022, which rendered part of it unusable. In this news report, it was claimed that the bridge was sabotaged by explosives planted under the sea due to the fluctuations in the sea surface just before the bridge exploded and that the unmanned naval vehicles given to Ukraine by the US may have been used for this purpose. At the same time, the article also shared photos taken by Russian media of the discovery of an unmanned naval vehicle allegedly given to Ukraine by the United States in September 2022 on the coast of Sevastopol in Crimea.
Similarly, in the attack on the Russian naval base in Sevastopol on October 29, 2022, unmanned aerial vehicles as well as unmanned naval vehicles were used. In the related news article, it is emphasized that Ukraine is planning to expand the use of UNVs, which are undetectable by Russian radars, in missions such as reconnaissance surveillance, base defence and convoy security.
Considering the approach of the three great powers to the issue, the US allocates considerable budgets for UNVs and tries to cover the deficit of its navy, which is numerically small compared to China, in this way.
On the other hand, the Chinese Navy intends to use UNVs for maritime reconnaissance/surveillance, mine and submarine warfare and mine countermeasures, and surveillance of submarine cables. It has also been suggested that China could use its planned UNVs to damage undersea fiber optic cables in a future conflict near Northern Taiwan, thereby disrupting trans-Pacific data exchanges that facilitate global Internet access.
On the other hand, Russia plans to use UNVs for effective oceanographic mapping of the Arctic and surrounding waters and to protect its submarines against advanced torpedo and mine threats from NATO member states. In terms of technology, Russia is the only country in the world that has succeeded in integrating nuclear turbine generators into UAVs and small underwater vehicles and has used this technology in its Poseidon strategic intercontinental autonomous torpedo. The 20-meter-long torpedo, which is currently being tested in the Arctic Sea and has a speed of 70 knots, a range of 10,000 kilometers and conventional/nuclear warhead options, can be fired from Belgorod-class nuclear submarines.
In conclusion, the use of UNVs will continue to increase in the future, both in defence and security and in scientific fields. Therefore, it can be stated that countries that develop themselves in this military field will emphasize this issue as an element of deterrence.
 Yen-Chiang Chang vd., “The International Legal Status of the Unmanned Maritime Vehicles”, Marine Policy, 113, 2020, p. 4.
 Missy Ryan-Dan Lamothe, “Pentagon: Chinese Naval Ship Seized an Unmanned U.S. Underwater Vehicle in South China Sea”, The Washington Post, https://www.washingtonpost.com/news/checkpoint/wp/2016/12/16/defense-official-chinese-naval-ship-seized-an-unmanned-u-s-ocean-glider/, (Date of Accession: 05.01.2023).
 Joanna Plucinska, “Nord Stream Gas ‘Sabotage’: Who’s Being Blamed and Why?”, Reuters, https://www.reuters.com/world/europe/qa-nord-stream-gas-sabotage-whos-being-blamed-why-2022-09-30/, (Date of Accession: 05.01.2023).
 “Sitrep on Nord Stream 1 and 2 Gas Pipelines”, The Saker, https://thesaker.is/sitrep-on-nord-stream-1-and-2-gas-pipelines/, (Date of Accession: 05.01.2023).
 Ashish Dangwal, “Kerch Bridge Attack: New Report Claims US Supplied UUVs Could be Behind the Explosion&Not Truck Bomb”, The Eurasian Times, https://eurasiantimes.com/kerch-bridge-attack-new-reports-claim-us-supplied-uuvs/, (Date of Accession: 05.01.2023).
 Emir Bilgen, “Ukrayna’nın Erken Savaş Ürünü: İnsansız Deniz Aracı”, Mavi Vatan, https://mavivatan.net/ukraynanin-erken-savas-urunu-insansiz-deniz-araci/, (Date of Accession: 06.01.2023).
 Hugo Patin, “Unmanned Underwater Vehicles: A Strategic Opportunity”, Grey Dynamics, https://greydynamics.com/unmanned-underwater-vehicles-a-strategic-opportunity/, (Date of Accession: 06.01.2023).
 Jim Sciutto, “US Observed Russian Navy Preparing for Possible Test of Nuclear-Powered Torpedo”, CNN, https://edition.cnn.com/2022/11/10/politics/us-russia-possible-torpedo-test, (Date of Accession: 06.01.2023).