In recent weeks, three Chinese research vessels have drawn media scrutiny after being spotted off the coasts of Australia and the Philippines. Although their exact activities remain unclear, their presence sparked concerns due to the documented dual-use nature of Chinese research, which is known to serve both civilian and military applications.
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The Australian media labeled it a Chinese “spy ship".The research vessel Tan Suo Yi Hao raised eyebrows in Australia’s media and political sphere after being spotted off the coast of South Australia in late March.
Local New Zealand reports indicate the vessel had been involved in a joint research project with New Zealand from January to March, “collecting samples from the bottom of the Puysegur trench", a deep cleft located south of the country.
What surprised analysts, though, was its homeward route: instead of a straightforward path east of Australia, it opted to circle the country from the west.
This vessel houses the Fendouzhe submarine, which New Zealand’s National Institute of Water and Atmospheric Research calls “the only research-focused submersible in the world currently able to dive to the deepest parts of the oceans".
Australian media quickly raised concerns that the vessel might be “spying” on Australia or“mapping critical underwater infrastructure”. When questioned by journalists on March 31, Australian Prime Minister Anthony Albanese said he “would prefer that it wasn’t there", and that Australia was “keeping an eye on this".
In response, China’s Foreign Ministry Spokesperson asserted that they were conducting “normal activities at sea in accordance with international law", urging Australia to “stop the groundless suspicion and speculations".
This happened just after Albanese called a national election, making waves in the Australian election campaign.
‘Things in China are rarely for purely scientific reasons’
The FRANCE 24 Observers team spoke with Ray Powell, the director of SeaLight, a maritime transparency project at the Gordian Knot Center for National Security Innovation at Stanford University in California. He explained why this vessel sparked concerns:
The reason why people get so disturbed is because all [Chinese] research vessels are assumed to be dual-use, and to play a role in co-ordinating with the People's Liberation Army [Editor’s note: China’s army].
Why is China interested in the coast of New Zealand and Australia? It may be for purely scientific reasons, but things in China are rarely for purely scientific reasons. For example, the deep sea is also a place that would be of great interest to China's submarine force.
Under Chinese law, all civilian agencies are required to co-operate with the military if they need co-operation.
Submarines rely on the ocean floor relief to navigate and hide; therefore, understanding the seabed's shape and composition is essential.
A January 2024 analysis by the Center for Strategic and International Studies (CSIS), a US-based think-tank, examined 64 Chinese research vessels operating in the Indian Ocean between 2020 and 2023.
The study focused on three key indicators that could suggest potential military ties: ownership by state-affiliated organisations with close links to the Chinese military, documented military port visits, and observed suspicious at-sea behaviour.
Their findings revealed that 52 of the 64 vessels exhibited at least two of these warning indicators, with a majority showing all three.
Vessel considered 'risky'
The FRANCE 24 Observers team spoke to Aidan Powers-Riggs, one of the study authors, who said that the Tan Suo Yi Hao was classified as "risky" based on all three indicators.
Regarding the first criterion, it is possible to find more information about the vessel ownership online. The Equasis database indicates that it is owned by the Chinese Institute of Acoustics, which is part of the Chinese Academy of Sciences.
These institutions appear to have ties to the Chinese military. As mentioned in the CSIS analysis, the Chinese Academy of Sciences has signed co-operation agreements with the People's Liberation Army (PLA).
Thewebsiteof the Institute of Acoustics also specifically refers to some historic connections with the PLA, mentioning, for instance, that it was transferred in 1967 “to be led by the 7th Institute of the Chinese PLA”.
The Chinese versionof the websitealso states that the institute “focuses on the strategic needs of China in the fields of ocean and security [...] over the next five to 10 years".
Powers-Riggs said:
The Chinese Institute of Acoustics has clear ties with the PLA given the importance of acoustic research for naval operations.
It's not to say that everything that the Institute of Acoustics is doing is for the Navy. Not at all. They certainly do a lot of genuine scientific research that has no military application. However, the point is that there are certainly ties. And if there is anything that they're doing that does have strategic applications, there's absolutely nothing stopping the PLA and China's Navy from being able to access and benefit from it.
The [Chinese] Navy is trying to catch up: it feels that it's behind, and it's being prioritised. So it's almost impossible that there aren't some pretty big mechanisms for collaboration.
Port calls made by the ship are another element that could spark suspicions. According to MarineTraffic, it made 163 port calls at Sanya, in China, between 2016 and 2024. This port is considered a “military-affiliated facility” in the CSIS analysis.
Powers-Riggs explained:
While individual port calls can be explained by a number of unrelated factors, in the aggregate, port calls are an important indicator in understanding a vessel's broader "pattern of life". Seeing a vessel make regular calls or have its base of operations at military-affiliated facilities is a warning sign that it could be involved in research projects or data and personnel exchanges with PLA entities.
Regarding the third criterion, Powers-Riggs said that at the time of the CSIS study, they had noticed “suspicious” behaviours.
Generally, it means going dark [Editor’s note: turning off automatic identification system (AIS) signals] for extended periods, either close to Chinese military explanations either in the South China Sea or close to the Philippines, Vietnam or Japan, or in the exclusive economic zones of other countries, which indicates that it is potentially conducting operations that it does not want to be watched.
Mapping submarine cables?
But what do we know about the vessel's current activities south of Australia?
While it is hard to know what is happening on board currently, analysts are trying to figure it out by looking at its AIS data, which tells us where it's been.
After following the southern Australian coast, the vessel stopped twice on April 7, 2025, between 550 and 630 nautical miles (about 1,020 to 1,170 km) from Australia’s south-west coast, “first for 12 hours and then for 17 hours", as Powell, the director of the maritime transparency project SeaLight, pointed out on X.
These stops occurred over the Diamantina Trench, where the vessel and the Fendouzhe submersible previously operated in January 2023. CGTN, the English-language news channel of state-run China Global Television Network, reported at that time that this marked “the first time in human history to reach the deepest point of the Diamantina Trench, which is of great significance to the development of the global abyss science".
Importantly, these stops were well outside Australia's Exclusive Economic Zone, meaning the vessel is allowed to conduct research under international law.
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Based on this trajectory, Powell said the hypothesis of the vessel mapping submarine cables is “doubtful". “There's no reason to run cables this deep in the ocean,” he said.
Dr Richard Dunley, a senior lecturer in history of maritime strategy at the University of New South Wales, also told the FRANCE 24 Observers team:
If it were doing survey work and mapping the sea floor, it would have been going much slower. It would have also likely followed a kind of grid pattern [Editor’s note: or “lawnmower pattern”], in which it would have gone back and forth and back and forth over a kind of box area … We didn't see any of that kind of behaviour.
Also, apart from a short period of time around eastern Australia, it was actually a lot further south of the Australian continent than most of this kind of marine infrastructure actually is. Very little deep or further down into the sub-ocean, there's just nothing there. So they weren't actually going anywhere that was particularly sensitive.
Facilitating the deployment of China’s submarine force?
According to Powell, the stops made by the vessel allow us to assume that the submersible it is carrying on board is being deployed.
He said the most “obvious” rationale for this operation would be to gather data to ultimately facilitate deployment of China’s submarine force, including its nuclear ballistic missile submarines.
Of course, it could be doing scientific research, and it is probably doing some scientific research. So if it is doing research, it may be just scientific research, but it also could be of use to the submarine force.
If you're looking for places to put a ballistic missile submarine, you often will want a lot of information about what's deep in the ocean.
But for Dr Richard Dunley, this explanation doesn’t hold up:
China has very few ballistic missile submarines. They are very important to China. China will defend those to the utmost, and it will operate them in a place where they can potentially launch missiles against the United States if necessary. There is absolutely no strategic rationale for them to send a ballistic missile submarine into the Indian Ocean, let alone into the deep south of the Indian Ocean, into the middle of nowhere. It is just utterly irrational. It is not going to happen.
'Civil-military fusion'
Dr Richard Dunley does stress that it is widely accepted that similar vessels deployed by China are dual-use, but he remains cautious about this specific case:
There's been a lot of talk in Australia about the fact that this is a spy vessel. I don't agree with that interpretation. Or at least I don't see any evidence at the moment that what it is doing is the sorts of things that people are claiming that it might be doing.
That is not to say that China doesn't use vessels like this to do exactly that kind of thing. In terms of guidance here in Australia, we are told that when engaging with these kinds of institutes, we have to be very careful because it's virtually impossible to guarantee that the information doesn't get back to some sort of military use.
With the United States or other Western countries, there's generally a pretty significant firewall between what's purely civilian research and military research. Whereas in China, they have something that we call civil-military fusion, where almost everything that is done on the civilian side, if there is a military application, it's generally assumed to be dual use.
The point here is that there is no evidence that is taking place at this time.
The Song Hang, a 'fishery survey vessel' spotted across the Philippines' archipelagic waters
The Tan Suo Yi Hao is not alone in attracting attention.
In recent days, the Chinese research vessel Song Hang has also come under scrutiny. In early April, it was observed navigating through the Philippines' archipelagic waters, prompting concern among Filipino media and analysts.
Jay Tarriela, Philippine Coast Guard (PCG) Spokesperson on West Philippine Sea Concerns stated on X that the vessel told the PCG that their plan was “to transit through the Sibutu Passage en route to the Indian Ocean" to "conduct fishing activities".
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However, the vessel's observed trajectory has led analysts, including Powell, to raise doubts about this stated purpose.
When it went through the Philippines' archipelagic waters, it didn't go in a straight line like other shipping does [...] It took a long detour first to the East and then over to the West and then eventually got started going back to the South again. There's no obvious reason for a transiting vessel to take that long, circuitous route.
“There are more direct routes available, particularly ones that do not require navigating along Taiwan's eastern coast or through the Philippine archipelagic waters,” also said Power-Riggs.
A closer look at the ship's route reveals it didn't follow the “lawnmower pattern” typically seen in detailed seabed mapping surveys.
However, as Powers-Riggs pointed out, that doesn't rule out other research activities.
There is quite a lot of valuable information that can be collected short of conducting lawnmower surveys. Depending on the equipment on board, a vessel could still collect data on water salinity, temperature, currents, undersea acoustics, and other factors without following a distinctive pattern. Without more information on what equipment is present on the Song Hang [...], it is difficult to say with certainty what data it could have collected.
It was noted by both experts that the vessel's course took it through regions that could be of interest to China. Powell said:
China is intensely interested in Taiwan and the ability to send ships through the Bashi Channel, [which is] between Taiwan and the Philippines. China's submarines have very poor access to deep water because China doesn't have a lot of deep water off its coasts. So, being able to map out that area to see where submarines might be able to pass and what the hazards are would be of intense interest.
Powers-Riggs also highlighted another key strategic location further south: the Lombok Strait, which links the South China Sea to the Indian Ocean.
The Lombok Strait is one of the only straits that is deep enough that submarines can go through it completely submerged and without having by international law to surface and thereby expose their location. So if you want to get from the South China Sea into the Indian Ocean, unless you want to go all the way around and take a pretty circuitous route, the best way is through the Lombok Strait.
The Zhong Shan Da Xue, a research vessel with a strange navigation path between Taiwan and the Philippines
A few days later, on April 2, the Zhong Shan Da Xue, another Chinese research vessel, was observed entering the Philippines' Exclusive Economic Zone (EEZ).
Philippine Coast Guard Spokesperson stated on X that the vessel was following “a pattern resembling a reversed ‘D’”, inferring that it was “likely conducting marine scientific research".
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Powers-Riggs also told our team that “a trajectory of that nature does suggest that some kind of research operation took place".
The vessel's background raises additional concerns. Powers-Riggs told our team that CSIS researchers classified it as "risky" based on their three criteria.
First, the vessel's history suggests potential ties with the Chinese military, while demonstrating just how blurred the lines are between civilian and military shipbuilding.
A2022 article from maritime publication Baird Maritimereports that the ship was designed by the 708th Research Institute of China State Shipbuilding Corporation(CSSC).
Powers-Riggs explained:
The 708th Research Institute is a subsidiary of CSSC, which is China's primary naval shipbuilder. It was involved in the design and construction of the Yuanwang-class tracking ships used by the PLA to track missiles, rockets, and spacecraft. More broadly, all institutes under the CSSC umbrella operate under the authority of the State-owned Assets Supervision and Administration Commission of the State Council (SASAC), meaning that all are ultimately responsive to state requests.
The firm's umbrella company was placed on the US Treasury Department's Non-SDN Chinese Military Industrial Complex (CMIC) list in 2021.
It's also important to note that the Jiangnan Shipyard, where the vessel was built, is "one of China's key dual-use shipyards, constructing both commercial and naval vessels", as Powers-Riggs points out.
Furthermore, the Equasis database lists Sun Yat-sen University (SYSU) as the vessel's owner, a detail also highlighted by the CSIS researcher.
SYSU has deep ties with the PLA, including hosting a supercomputer used by the National University of Defence Technology to test nuclear weapons systems, and operating dual-use platforms like the Zhu Hai Yun research vessel.
Data from MarineTraffic shows the vessel visited Sanya’s port five times in 2023.
Powers-Riggs said the CSIS researchers had also flagged the vessel for having “lots of dark activity in the South China Sea, particularly near the Paracel Islands [Editor’s note: a disputed archipelago claimed by China, Taiwan and Vietnam, and currently controlled by China], close to China's military installations and militarised islands".
In this case, too, we do not know precisely what sort of operations the vessel was conducting.
But the experts say the region is definitely of interest to China.
The ship was again operating near the strategic Bashi Channel. It also went close to the Batanes Islands, a group of islands located at the northernmost tip of Philippine territory, and the same place where US Defence Secretary Pete Hegseth just announced that advanced joint Special Operations Forces training would take place. “So it would make sense that China would be especially interested in that area,” Powell said.
A key point is that both the Song Hang and the Zhong Shan Da Xue entered the Philippine Exclusive Economic Zone. Conducting research there, if it happened, would be illegal under the United Nations Convention on the Law of the Sea, which requires permission for such activities in another nation's EEZ.
'China has an increasing number of these research vessels'
According to these analysts, these recent incidents fit a larger pattern, as Powell explained:
China has an increasing number of these research vessels, and they are sending them further and further abroad. We're seeing a lot of them, for example, in the Indian Ocean and in the deep Pacific.
Dr Richard Dunley also highlighted the challenges it could pose:
I would be quite surprised if we don't see more activity from the Chinese Navy generally, and from survey vessels in the next five years, in the waters of Australia.
And the reality is that under the UN Convention on the Law of the Sea, they can absolutely do that in waters beyond 200 nautical miles. And it will be very difficult for Australia to prevent them from doing it inside its exclusive economic zone, the area inside 200 nautical miles, unless there is a very good reason. So Australia would have a difficult decision to make. Do they kind of follow the letter of the law, or do they try and push back?
