Yellow Sea Construction
The Yellow Sea is a tough neighborhood.
May 20, 2025
This is an analysis of the Yellow Sea, also known as the West Sea by the Koreas, between China, North Korea, and South Korea.
We understand that in 2024, the People's Republic of China (PRC or just China) built three temporary structures in the Yellow Sea in a significant change to the status quo. One is a mobile steel framework exceeding 50 meters in diameter and height that used to be an oil drilling rig used in the Middle East, and has facilities to house personnel (estimated from 70 - 100, with a helipad and vessel docking facilities). The second and third structures float, and are described as fish farms. The three are described by China as Fishing Support Facilities. South Korean Intelligence reported on January 9, 2025 that China had installed a steel structure in the Provisional Measures Zone (PMZ) of the Yellow Sea. The location is still undisclosed, and we cannot yet access imagery of the three platforms via Google Earth. 1
The PMZ is the place where the exclusive economic zones (EEZs) overlap (roughly in the middle of the Yellow Sea). It was created to settle potential disputes in 2001 by South Korea and China. It delineates joint fishing rights and fisheries management.
South Korea has recently asked that these three temporary structures be removed from the South Korean EEZ. China has refused, but has agreed to not build additional structures.
This is an analysis of the Yellow Sea, also known as the West Sea by the Koreas, between China, North Korea, and South Korea.
We understand that in 2024, the People's Republic of China (PRC or just China) built three temporary structures in the Yellow Sea in a significant change to the status quo. One is a mobile steel framework exceeding 50 meters in diameter and height that used to be an oil drilling rig used in the Middle East, and has facilities to house personnel (estimated from 70 - 100, with a helipad and vessel docking facilities). The second and third structures float, and are described as fish farms. The three are described by China as Fishing Support Facilities. South Korean Intelligence reported on January 9, 2025 that China had installed a steel structure in the Provisional Measures Zone (PMZ) of the Yellow Sea. The location is still undisclosed, and we cannot yet access imagery of the three platforms via Google Earth. 1
The PMZ is the place where the exclusive economic zones (EEZs) overlap (roughly in the middle of the Yellow Sea). It was created to settle potential disputes in 2001 by South Korea and China. It delineates joint fishing rights and fisheries management.
South Korea has recently asked that these three temporary structures be removed from the South Korean EEZ. China has refused, but has agreed to not build additional structures.
The Yellow Sea, Google Earth, 5/21/2025
Notation is ours.
What do we know about the Yellow Sea?
- It is shallow, relatively speaking, and is located between China and the Koreas.
- In 2001 an agreement was reached on how to work together, bilaterally, between South Korea and China.
- In 2015, agreements were made to continue negotiating the use of the Yellow Sea.
- It is potentially rich with resources, including fish and crabs (fishing, energy).
- This body of water is in close proximity to major South Korean population centers like Incheon and Seoul.
"Since 2013, China has been unilaterally insisting that the maritime operational demarcation with South Korea be set along the 124°E meridian line. South Korea has proposed the demarcation be equidistant between the two coasts, which would be west of the Chinese demarcation. Since late 2024, Chinese military and aquacultural activities in the Yellow Sea has increased, although not all statistics show an increase (e.g., military vessel incursions into South Korea's EEZ but not territorial waters has stabilized at about one per day). 2 We have read that South Korea is conducting parallel incursions with their navy and air force to maintain the status quo (so a tit-for-tat strategy).
- It is shallow, relatively speaking, and is located between China and the Koreas.
- In 2001 an agreement was reached on how to work together, bilaterally, between South Korea and China.
- In 2015, agreements were made to continue negotiating the use of the Yellow Sea.
- It is potentially rich with resources, including fish and crabs (fishing, energy).
- This body of water is in close proximity to major South Korean population centers like Incheon and Seoul.
"Since 2013, China has been unilaterally insisting that the maritime operational demarcation with South Korea be set along the 124°E meridian line. South Korea has proposed the demarcation be equidistant between the two coasts, which would be west of the Chinese demarcation. Since late 2024, Chinese military and aquacultural activities in the Yellow Sea has increased, although not all statistics show an increase (e.g., military vessel incursions into South Korea's EEZ but not territorial waters has stabilized at about one per day). 2 We have read that South Korea is conducting parallel incursions with their navy and air force to maintain the status quo (so a tit-for-tat strategy).
There was violence between Chinese fishermen and the South Korean Coast Guard in 2016.
On September 29, 2016, three Chinese fishermen died when their boat caught on fire after being fired upon (stun grenades) by the South Korean coast guard for illegal fishing.
On October 7 2016, Chinese fishing boats collided with a South Korean coast guard speed-boat in the Yellow Sea, and after a few hits or rammings, the coast guard speed-boat sunk. The crew was rescued by another South Korean vessel nearby. What happened was that Chinese Fishermen were fishing in South Korean waters 40 nautical miles from Korea's coast (allegedly).
After this incident, South Korea refined its military procedures to allow for greater freedom of action in response to angry fishermen. It amended its Maritime Security Act and its Manual on the Use of Weapons on November 8, 2016 China's advice to South Korea was to stay "reasonable and cool-headed."
In November 2016, The South Korean Coast Guard opened fire on a Chinese fishing vessel after it attempted to ram the coast guard vessel.
According to the Diplomat, "illegal Chinese fishing had been a constant irritant between South Korea and China, leading to the deaths of both KCG officers and Chinese fishermen. In early October, a Chinese fisherman was killed during a scuffle with the KCG 90 miles west of Wangdeung-do island. In September, three Chinese fishermen died trying to evade arrest after KCG officials fired flares and non-lethal stun grenades into the vessel’s wheel-house where Chinese fishermen had locked themselves in. In December of 2010, a Chinese fisherman died while attempting to repel KCG officers from boarding their fishing vessel. Since 2008, two KCG officers have been killed by Chinese fishermen and 73 injured during attempted arrests of Chinese fishing vessels in Korea’s EEZ." 7
On September 29, 2016, three Chinese fishermen died when their boat caught on fire after being fired upon (stun grenades) by the South Korean coast guard for illegal fishing.
On October 7 2016, Chinese fishing boats collided with a South Korean coast guard speed-boat in the Yellow Sea, and after a few hits or rammings, the coast guard speed-boat sunk. The crew was rescued by another South Korean vessel nearby. What happened was that Chinese Fishermen were fishing in South Korean waters 40 nautical miles from Korea's coast (allegedly).
After this incident, South Korea refined its military procedures to allow for greater freedom of action in response to angry fishermen. It amended its Maritime Security Act and its Manual on the Use of Weapons on November 8, 2016 China's advice to South Korea was to stay "reasonable and cool-headed."
In November 2016, The South Korean Coast Guard opened fire on a Chinese fishing vessel after it attempted to ram the coast guard vessel.
According to the Diplomat, "illegal Chinese fishing had been a constant irritant between South Korea and China, leading to the deaths of both KCG officers and Chinese fishermen. In early October, a Chinese fisherman was killed during a scuffle with the KCG 90 miles west of Wangdeung-do island. In September, three Chinese fishermen died trying to evade arrest after KCG officials fired flares and non-lethal stun grenades into the vessel’s wheel-house where Chinese fishermen had locked themselves in. In December of 2010, a Chinese fisherman died while attempting to repel KCG officers from boarding their fishing vessel. Since 2008, two KCG officers have been killed by Chinese fishermen and 73 injured during attempted arrests of Chinese fishing vessels in Korea’s EEZ." 7
Using the Copernicus Browser, we can see some tiny specks in the PMZ between PRC and S.K. in the Yellow Sea. When we zoom in, they all look like ships except one structure at 34.93694, 122.71229. Using False Color, we see this structure and two ships due northeast sailing south past it.
Copernicus Browser, 5/22/2025 imagery, using False Color (Bands B8, B4 and B3). 500m resolution.
When we zoom in a little closer (300m resolution), we start to see an identifiable shape in the water, again False Color, Copernicus Browser.
The object is gone on 5/2/2025 (20 days before the latest imagery), and we see a ship transiting the area from West to East (China to South Korea). We had read that two of the three maritime features were fully submersible (they are fish farms).
On 5/12/2025, we see a different white mark (chalk line) at 34.93601, 122.75203. You can see it with True Color at 100m resolution, along with a southbound ship trailing a wake, and
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We see another spot at 34.97961, 123.20086 worth noticing in the water, with many ships passing northbound and southbound at a 1km resolution, taken on 5/12/2025. Looks like a chalk mark (white on a grey sea) in a line, one slash, then water, then two slashes close to each other.
In conclusion of our review using imagery, there are specks and chalk lines in the Yellow Sea where the newspapers suggested we look, but nothing appears permanent or large or permanent enough to register.
The three maritime structures
The picture below is a fixed maritime structure installed by China in the PMZ in the Yellow Sea. It is on their side of the Operational Demarcation Line at 124 degrees east. It is 100 meters in width, 80 meters long, and rises 50 meters high, and has three steel bridges and a helipad. China calls it a "fish farm support facility." It may house as many as 100 personnel, and tends to be busy with vessels docked alongside.
The Chosun Daily found: "A ship registry search revealed the structure was originally built in France in 1982 and operated as an oil drilling rig in the Middle East and other regions before its decommissioning in 2016." The location is estimated as follows: In contrast, the fixed platform—converted from the decommissioned oil rig—has remained anchored since its installation near 35 degrees north latitude and 122 degrees east longitude in October 2022.
This is one of three facilities in this area, with the other two named Shenlan-1 and Shenlan-2. Shenlan-2 lies about 3 km to the Southeast, and is described by China as a new-model fish farm. It was deployed in May 2024.
The picture below is a fixed maritime structure installed by China in the PMZ in the Yellow Sea. It is on their side of the Operational Demarcation Line at 124 degrees east. It is 100 meters in width, 80 meters long, and rises 50 meters high, and has three steel bridges and a helipad. China calls it a "fish farm support facility." It may house as many as 100 personnel, and tends to be busy with vessels docked alongside.
The Chosun Daily found: "A ship registry search revealed the structure was originally built in France in 1982 and operated as an oil drilling rig in the Middle East and other regions before its decommissioning in 2016." The location is estimated as follows: In contrast, the fixed platform—converted from the decommissioned oil rig—has remained anchored since its installation near 35 degrees north latitude and 122 degrees east longitude in October 2022.
This is one of three facilities in this area, with the other two named Shenlan-1 and Shenlan-2. Shenlan-2 lies about 3 km to the Southeast, and is described by China as a new-model fish farm. It was deployed in May 2024.
Atlantic Amsterdam Morrovia - Chinese Fixed Maritime Platform in the Yellow Sea PMZ
This photo, taken on Feb. 26 by the Onnuri, a research vessel operated by the Korea Institute of Ocean Science and Technology, shows a large fixed platform installed by China in the Yellow Sea’s Provisional Measures Zone. The steel structure, which Beijing claims is a “fish farm support facility,” measures 100 meters in width and 80 meters in length and features three steel bridges and a helipad. This is the first publicly released image of the unauthorized platform. /Courtesy of Korea Institute of Ocean Science and Technology, Rep. Um Tae-young 6
At the time this photo above was taken, South Korea's Onnuri attempted to approach the Chinese platform for inspection. There was a rubber boat with knife-wielding men sent to intercept the Onnuri. From there, a stand-off occurred between South Korean and Chinese coast guard ships for two hours. The South Koreans are not welcome.
At the time this photo above was taken, South Korea's Onnuri attempted to approach the Chinese platform for inspection. There was a rubber boat with knife-wielding men sent to intercept the Onnuri. From there, a stand-off occurred between South Korean and Chinese coast guard ships for two hours. The South Koreans are not welcome.
The picture below shows Shenlan-2, which is described by China as a fish farm. According to Chosun Daily, "analysis of satellite photos from the past three years indicates that Shenlan-1 and Shenlan-2—described by China as advanced fish farms—are semi-submersible. They are visible while afloat but disappear from satellite view when submerged, with indications that they may be capable of relocating underwater."
Shenlan-2 Platform surveillance tower. The main body of the structure is below the surface of the water.
The picture below is Shenlan-1, which is also described as a floating fish farm.
"According to the Ministry of Foreign Affairs on the 24th, the issue of China's structures in the Yellow Sea was addressed during the third maritime cooperation dialogue held in Seoul the day before between South Korea and China. China installed deep-sea aquaculture facilities, named the Seonran No. 1 (2018) and Seonran No. 2 (2024), in the provisional measures area where the two countries' 200 nautical mile exclusive economic zones (EEZs) overlap. In 2022, it also built structures in the form of oil drilling facilities, claiming they were management facilities." 5
"According to the Ministry of Foreign Affairs on the 24th, the issue of China's structures in the Yellow Sea was addressed during the third maritime cooperation dialogue held in Seoul the day before between South Korea and China. China installed deep-sea aquaculture facilities, named the Seonran No. 1 (2018) and Seonran No. 2 (2024), in the provisional measures area where the two countries' 200 nautical mile exclusive economic zones (EEZs) overlap. In 2022, it also built structures in the form of oil drilling facilities, claiming they were management facilities." 5
Shenlan-1 with a ship or two alongside. China installs the large steel framework structure Xianlan No. 1 in the Yellow Sea's temporary adjustment area. /Courtesy of social media (SNS) capture.
Here is another view of Shenlan-1.
Another view of Shenlan-1. China is building structures in the middle of the Yellow Sea (Image: Xinhua/Li Ziheng)
China and South Korea are operating under a maritime cooperation framework. "South Korea and China agreed to establish the 'Marine Order Subcommittee' under the maritime cooperation dialogue to address conflict issues such as structures in the Yellow Sea and illegal fishing, and the 'Practical Cooperation Subcommittee' to address cooperation issues such as joint juvenile releases and search and rescue, continuing their communication."
"The South Korea-China maritime cooperation dialogue was established in December 2019 through an agreement between the foreign ministers of both countries. The first meeting was held in April 2021, followed by the second meeting in June of the following year. The two countries are also scheduled to hold the fourth maritime cooperation dialogue in China."
Diplomats from the United States and Japan have commented on the unilateral building of temporary structures in the Yellow Sea as a potential escalation of maritime claims, similar to what has occured in the South China Sea.
"The South Korea-China maritime cooperation dialogue was established in December 2019 through an agreement between the foreign ministers of both countries. The first meeting was held in April 2021, followed by the second meeting in June of the following year. The two countries are also scheduled to hold the fourth maritime cooperation dialogue in China."
Diplomats from the United States and Japan have commented on the unilateral building of temporary structures in the Yellow Sea as a potential escalation of maritime claims, similar to what has occured in the South China Sea.
South Korea's Leodo Ocean Research Station
This sits 149 kilometers from South Korea's Marado Island (populated island), and 247 kilometers from the nearest Chinese island.
This sits 149 kilometers from South Korea's Marado Island (populated island), and 247 kilometers from the nearest Chinese island.
Military Activities Increase by China
The Chinese PLAN has been training, patrolling and operating within the South Korean EEZ, but not within South Korea's territorial waters. According to the Joint Chiefs of Staff to Representative Eom Tae-young of the People Power Party, Chinese warships entered the S.K. jurisdictional sea area over 330 times in 2024, and over 100 incursions so far by April 29, 2025. This is a significant increase over 2017 (110) and 2018 (230), 2019 (290), 2020-2022 (200), and 2023 (360).
The majority of the vessels involved were destroyers and frigates affiliated with the PLA North Sea Fleet Command, based in Qingdao, Shandong Province and were conducting training exercises. Submarines from the same fleet were also detected operating within S. Korea’s jurisdictional waters, according to military officials.
South Korea is concerned that China sees the Yellow Sea as important for any crises in the Taiwan Strait. China is concerned that the Yellow Sea holds strategic military importance for South Korea as the home to the Navy’s Second Fleet and home to the U.S. Military’s Camp Humphreys.
China has requested that South Korean naval vessels avoid operating west of the 124th meridian east to avoid potential conflicts.
The Chinese PLAN has been training, patrolling and operating within the South Korean EEZ, but not within South Korea's territorial waters. According to the Joint Chiefs of Staff to Representative Eom Tae-young of the People Power Party, Chinese warships entered the S.K. jurisdictional sea area over 330 times in 2024, and over 100 incursions so far by April 29, 2025. This is a significant increase over 2017 (110) and 2018 (230), 2019 (290), 2020-2022 (200), and 2023 (360).
The majority of the vessels involved were destroyers and frigates affiliated with the PLA North Sea Fleet Command, based in Qingdao, Shandong Province and were conducting training exercises. Submarines from the same fleet were also detected operating within S. Korea’s jurisdictional waters, according to military officials.
South Korea is concerned that China sees the Yellow Sea as important for any crises in the Taiwan Strait. China is concerned that the Yellow Sea holds strategic military importance for South Korea as the home to the Navy’s Second Fleet and home to the U.S. Military’s Camp Humphreys.
China has requested that South Korean naval vessels avoid operating west of the 124th meridian east to avoid potential conflicts.
Proportional Military Response 4
Given China’s posture, South Korea has engaged a proportional response strategy. Each time a Chinese warship crosses the median line into waters under South Korea’s jurisdiction, a South Korean naval vessel will do the same—enter waters claimed by China. Such reciprocal action prevents Beijing from strengthening its de facto control.
A similar strategy is already being applied in the air. Since 2024, whenever a Chinese military aircraft enters the South Korean Air Defense Identification Zone (KADIZ), the South Korean military has responded by sending its own aircraft into China’s zone, known as CADIZ.
Given China’s posture, South Korea has engaged a proportional response strategy. Each time a Chinese warship crosses the median line into waters under South Korea’s jurisdiction, a South Korean naval vessel will do the same—enter waters claimed by China. Such reciprocal action prevents Beijing from strengthening its de facto control.
A similar strategy is already being applied in the air. Since 2024, whenever a Chinese military aircraft enters the South Korean Air Defense Identification Zone (KADIZ), the South Korean military has responded by sending its own aircraft into China’s zone, known as CADIZ.
All of this activity should be taken in the context of the ongoing relationship between North and South, and the 1953 Line of Demarcation or Northern Limit Line (a maritime boundary) that has not been agreed to by the DPRK. It creates a working relationship between the two nations. There has been violence between the two nations in the West Sea:
- Daecheong incident or the Battle of Daecheong caused somewhere between one and ten killed from DPRK. November 10, 2009
- ROKS Cheonan sinking. March 26, 2010. A DPRK minisub fired a torpedo and sunk the Pohang-class corvette of the ROK Navy. Of the 104 personnel, 46 seamen were killed.
- The First Battle of Yeonpyeong on June 15, 1999 was due to an incursion across the Northern Limit Line. Over the coming days, repeated and proportional violations of the line occurred. However, on June 9, there was an accidental collision. Then the ROK Navy started bumping the DPRK boats, damaging some of them. The DPRK navy was not as good at bumping, so they both brought out the military vessels. Somewhere between 17 to 30 to 100 DPRK sailors were killed and 9 South Korean sailors were injured. The South Koreans didn't mess around, and responded with overwhelming force, firing a total of 4,584 rounds of ammunition, including 20MM, 40MM and 76MM weapons over 14 minutes.
- The Second Battle of Yeonpyeong, June 29, 2002, was similar in that North and South Korean patrol craft engaged, there was a 34 minute battle, and 13 North Korean seamen were killed, while the South Koreans lost 6 seamen. The South Korean vessel, a PKM 357,s was recovered from the ocean floor and now sits in a museum.
Source for this section is Wikipedia, which has a page on each battle. Thank you Wikipedia en.wikipedia.org.
- Daecheong incident or the Battle of Daecheong caused somewhere between one and ten killed from DPRK. November 10, 2009
- ROKS Cheonan sinking. March 26, 2010. A DPRK minisub fired a torpedo and sunk the Pohang-class corvette of the ROK Navy. Of the 104 personnel, 46 seamen were killed.
- The First Battle of Yeonpyeong on June 15, 1999 was due to an incursion across the Northern Limit Line. Over the coming days, repeated and proportional violations of the line occurred. However, on June 9, there was an accidental collision. Then the ROK Navy started bumping the DPRK boats, damaging some of them. The DPRK navy was not as good at bumping, so they both brought out the military vessels. Somewhere between 17 to 30 to 100 DPRK sailors were killed and 9 South Korean sailors were injured. The South Koreans didn't mess around, and responded with overwhelming force, firing a total of 4,584 rounds of ammunition, including 20MM, 40MM and 76MM weapons over 14 minutes.
- The Second Battle of Yeonpyeong, June 29, 2002, was similar in that North and South Korean patrol craft engaged, there was a 34 minute battle, and 13 North Korean seamen were killed, while the South Koreans lost 6 seamen. The South Korean vessel, a PKM 357,s was recovered from the ocean floor and now sits in a museum.
Source for this section is Wikipedia, which has a page on each battle. Thank you Wikipedia en.wikipedia.org.
To be completed once we find satellite imagery...
Area
Yellow Sea
Maritime Features in the Yellow Sea
Nearest Land Qingdao, China
Distance from Land (miles) 217 km
Location (latitude & longitude) 34.93694, 122.71229
Diameter (miles) Zero
Date of Satellite Imagery 5/12/2025 (false color)
Airport Present? No
Helipad Present? Yes - but in press pictures not imagery.
Port / Dock Facility Present? Yes, in press pictures, not imagery.
Buildings Present? Yes, one with housing for up to 50-100 staff (press pictures)
Defensive Infrastructure Present? No
Athletic Facilities Present? No
Hospital Present? No
Sand Only Island? Floating or movable structures only...no dredging.
Dredging Infrastructure Only? No
Yellow Sea
Maritime Features in the Yellow Sea
Nearest Land Qingdao, China
Distance from Land (miles) 217 km
Location (latitude & longitude) 34.93694, 122.71229
Diameter (miles) Zero
Date of Satellite Imagery 5/12/2025 (false color)
Airport Present? No
Helipad Present? Yes - but in press pictures not imagery.
Port / Dock Facility Present? Yes, in press pictures, not imagery.
Buildings Present? Yes, one with housing for up to 50-100 staff (press pictures)
Defensive Infrastructure Present? No
Athletic Facilities Present? No
Hospital Present? No
Sand Only Island? Floating or movable structures only...no dredging.
Dredging Infrastructure Only? No
A few sources, and the rest we have bookmarked.
Source 1: Here, South Korea nervous over China encroaching in Yellow Sea by Debadrita Sur, May 13, 2025. Daily Express USA.
Source 2: Here, The Yellow Sea: An Overlooked Geopolitical Hotspot, Sang Hun Seok January 29, 2025, RUSI.ORG
Source 3: Source: 1945 Article here
Source 4: (opinion piece - link here)
Source 5: Here is another discussion in Chosun Biz, link here.
Source 6: Source: The Chosun Daily, link here.
Source 7: Link here, Morris, November 3, 2016, South Korea cracks down on illegal Chinese fishing, with violent results.
Source 1: Here, South Korea nervous over China encroaching in Yellow Sea by Debadrita Sur, May 13, 2025. Daily Express USA.
Source 2: Here, The Yellow Sea: An Overlooked Geopolitical Hotspot, Sang Hun Seok January 29, 2025, RUSI.ORG
Source 3: Source: 1945 Article here
Source 4: (opinion piece - link here)
Source 5: Here is another discussion in Chosun Biz, link here.
Source 6: Source: The Chosun Daily, link here.
Source 7: Link here, Morris, November 3, 2016, South Korea cracks down on illegal Chinese fishing, with violent results.
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