Instead, a large variety of corvette type classes, in the form of missile boats and submarine chasers fulfill the tasks of patrolling China's territorial waters.

Originally the units were waiting at Yongxing Island, but due to the problem of communications, they were not notified until the battle was already in progress.

[citation needed] Over 100 were built, but as newer submarine chasers enter service, this class is steadily being decommissioned.

[citation needed] In PLAN service, pennant numbers as follows: 601－610, 622, 625－629, 639, 650, 673, 674, 677, 681－687, 689－692, 694－696, 698－709 and 721－742[citation needed] The Haijiu class submarine chasers are two (possibly four) modified versions of the Hainan class submarine chasers (Type 037) of the People's Liberation Army Navy.

DIP 12, the VDS version weigh 4 tons and has a 200-meter cable with towing speed of 16 kn, and the range is selectable at 2, 4, 8 and 16 km respectively.

A total of six vessels were delivered to the PLA Navy and form the main naval defence force currently stationed in Hong Kong.

However, this specifications was too complicated for China, and a major redesign was begun, resulting in a boat with C-801 SSMs, diesel engines and propellers instead.

The OTO Melara 76 mm gun was retained in the revised design, called in 1988 the EH-3D (and in 1996 the 520T), but failed to survive the cooling of relations with the West following the Tiananmen Square protests of 1989 and the resulting end of Western participation in Chinese military projects.

However, due to technological difficulties (particularly with regards the license produced SEMT diesel engines), high price, and over sophisticated design compared to the PLAN standard, further production was terminated.

The first time in 2001 whilst on a pre-delivery test it was nearly sunk after a collision with a fast ferry servicing the Hong Kong-Guangzhou route.