The Type 645 oceanographic research ship is an oceanographic ship developed by China for the People's Liberation Army Navy (PLAN) and other Chinese civilian establishments.
However, on May 2, 1993, Xiangyanghong 16 was rammed and sunk by a Cypriot LNG carrier more than nine time of its size (38000 ton) in the East China Sea near Jeju Island, with the loss of three crew members.
The sister ships in civilian service are often tasked with military and paramilitary missions and thus frequently come under PLAN and Chinese Coast Guard control.
In addition to the original oceanographic research ship, the hull of Type 645 is used for both Type 812 and Type 813 spy ships, but the former was a failure due to excessive vibration preventing onboard intelligence gathering gears from working properly, and thus converted back to its original oceanographic research role.
The name of the unit in PLAN service is Nan-Diao (南调) 350, meaning South Investigate 350.