Must be done before opening the surface access hatch.
In the Tangoroa Storage Room (the one with the crane) there is a room underneath the generator platform. The door is directly underneath the crane control console.
Arrange the boxes to allow you to move into the room by moving boxes into free spaces repeatedly. Note that the yellow and black tape points to the side of the boxes that are open.
The achievement will pop as soon as you walk through the door.