On 21 June 2023, China's hydrographic research vessel Haiyang Dizhi Ba Hao (also known as Haiyang Dizhi 8, or HD8) began an extensive survey at Luconia Shoals on Malaysia's continental shelf--a project that has continued for over a month so far. 

This survey is almost certainly unauthorized by Malaysia, and is therefore illegal under the United Nations Convention on the Law of the Sea, which requires the surveyor to request consent six months in advance of such activities.

The HD8 is accompanied by three apparent maritime militia ships: Yue Mao Gang Yu 92777, Yue Zhan Yu 08046 and Yue Zhan Yu 08048. The AIS signals for these ships appear intermittently, indicating they are using the weaker Class-B transmitters, which are only detectable when a terrestrial or ship-borne receiver is in the area.

When they are detectable, the militia ships are frequently seen together with four other AIS signals: HU 02, HU 03, HU 04 and 12366812061. My current theory on this is that each militia ship is carrying a hydrographic survey array--either of different types or just spares of the same type for HD8. 

In this view from 20 July each of the three militia ships has one of these other signals in such close proximity they are virtually superimposed over one another, while the fourth (HU 03) trails 3.5 nautical miles behind the HD8 moving east.

The HD8's other constant companion is a China Coast Guard (CCG) ship, number 5202, which helps to screen it from the Royal Malaysian Navy (RMN) ships that come out to monitor the survey. 

Meanwhile, CCG 5402 is on its normal patrol, asserting China's claim of jurisdiction over Malaysia's gas fields to the east/southeast of the survey activity.

In this view of AIS signals taken today (23 July), both CCG ships may be seen, with the KD Keris (RMN 111) keeping an eye on the survey while KD Bunga Mas Lima (RMN AUX 5) monitors CCG 5402. (For clarity I have excluded other signals, including those of the militia ships & probable hydrographic equipment arrays.)

That China did not seek such consent for this survey is conjecture on my part, but it seems a safe bet since China asserts jurisdiction over Luconia Shoals as part of its nine-dash line claim. This is the reason the CCG patrols this area almost continuously--at least 316 days in 2022 according to the Asia Maritime Transparency Initiative. 

Thus Beijing could hardly seek Malaysia's consent, as that would be an admission that its claim of jurisdiction is illegal. 

Because of the way China conflates its military and commercial activities, its ultimate purpose(s) for this survey can only be guessed at, but it certainly advances Beijing's consistent claims of "indisputable sovereignty" over the "adjacent waters" to the Spratly Islands within the nine-dash line.

For its part, Malaysia's government has said little publicly about the activity since the early days of the survey.