Have you seen these things? They are massive, they can suck sand in huge quantities from the Sea Floor and then have a massive blow aperture that can then redeposit the sand at speed at the location that it is required. They are big, made from thick steel and are hugely heavy, especially when filled.
China has an Armada of these ships working around the clock almost, in the SCS.
My point is that if a Hostile fleet came into waters claimed as Territorial, by China, that they could put a lot of these in the way of that fleet to disrupt its cruising, While keeping the PLAN further back keeping a wary eye and the intrudes very much under its guns. If the hostile fleet threaten the Dredgers, they would be threatening unarmed Chinese civilian vessels in Chinese claimed Territorial Waters and this would elicit equally dire threats back.
Further of course, if one of these Steel Behemoths was to collide with a warship, it is the warship that would come of the worst.
In fact I remember a few years ago that a US Cruiser or Destroyer was nearly totaled by a Dredger in the SCS and only avoided collision by a just a few feet.
