The Glomar Explorer
maritime.orgI can neither confirm nor deny the existence of this ship.
You beat me to it!
When I was a work/study intern at Hughes in the late '70s, I worked with a guy who had worked on the Glomar Explorer. He was told that he was working on a program for outer space, and told his supervisors that the hardware was ridiculously overspecced. Of course, the HW did in fact need to withstand very high pressures that far under water.
I was never accessed to the Glomar Explorer program.