Research ships & seabed surveys: Inside China's grey

Seabed mapping: Collecting information underwater terrain and ocean conditions that can affect submarine operations.

Undersea cable intelligence: Identifying the location and vulnerability of cables carrying internet and communications traffic.

Surveillance: Observing military exercises and the movements of Taiwanese or allied forces.

Maritime claims: Repeatedly operating in contested waters to create an impression that China exercises authority there.

2024: Xiang Yang Hong 06 and seabed-mapping concerns

May 7, 2026: Taiwan challenges the Tongji

June 6-10, 2026: Chinese agencies conduct a maritime enforcement operation

June 16, 2026: Xiang Yang Hong 22 conducts a marine survey

June-July 2026: Coast guard patrols expand east of Taiwan

July 17-23, 2026: Lanhai 201's survey raises questions

August 10-31, 2026: China conducts a seabed survey east of Taiwan

Mid-August 2026: Three-vessel group spotted off Taiwan's east coast

Minfudingyu 07902 , identified as a Chinese fishing boat that doubles as a maritime militia vessel.

China Coast Guard cutter 2502.

Research vessel Xiang Yang Hong 03 .

September 3, 2026: Beijing acknowledges the August survey

October 8, 2026: Reuters reports the militia boat sighting

Okinawa Trough, north of Taiwan: An underwater region between Taiwan and the Ryukyu island chain.

Huatung Basin, east of Taiwan: An area relevant to understanding the seabed and ocean conditions off Taiwan's Pacific coast.

Luzon Trough and Manila Trench, south of Taiwan: Underwater features near routes linking the South China Sea and the western Pacific.

Operational familiarity: Repeated deployments can improve knowledge of sea routes, vessel movements and operating conditions.

Administrative pressure: Demands for shipping information can test whether Beijing can make commercial operators comply with its claims.

Normalisation: Regular patrols may gradually make a Chinese presence appear routine, even where Taiwan disputes China's authority.