The Glomar Explorer wasn't unique because of it's mobile derrick. There were any number of ships designed for that purpose. It was notable for its deep sea mining of exotic minerals, such as manganese. To date, there still isn't a ship capable of doing such a task and this particle ship was positioned in a public school textbook as having done so.
The ship was used by mining companies after its sub recovery cover was blown.
It's still being used now for oil drilling.