In early 2016 the Chinese Navy put its first self-propelled floating dry dock (Huachuan No. 1) into service. Huachuan enables ships of up to 20,000 tons to obtain relatively simple repairs (usually to the hull) that require the use of a dry dock without travelling back to port. These floating dry docks were very popular during World War II in the Pacific and the U.S. Navy had over a dozen of them. These were mostly towed, not self-propelled. The U.S. Navy retired the last of these (which mostly handled nuclear sub repairs) in 2001.
There are many commercial floating docks in service, many of them built in China. Like the new Chinese Navy floating dock these vessels (especially Huachuan) include space for workshops and personnel needed to make the repairs on ships and ship components as well.