Some of the floorboard has been removed to gain access to the crawl space. The old drain plumbing has been removed. What's left in its place is a small section of rubber hose where the old drain plumbing connected.
This was a bit of luck since the old pluming pipe ended at almost the exact location that it needs to be for the new shower drain location. If this house were built on a slab, this would all be underground work that needed to be excavated.