On Chapter 6 "The Fall", reach the 1971-era test facility and Cave will begin talking about testing on hobos. Below one of the test spheres and a giant Aperture logo is a room marked "CONTROL ROOM" with yellow letters. Use a portal to get high above the Control Room. Enter the small office. Enter the door behind the cabinet and follow the hidden hallway to a dock. At the end of the walkway, near the docks, is a orange life preserver marked "BOREALIS". Examine it and the achievement is yours.. Note: This is a reference to the Aperture ship "Borealis" that is seen at the end of Half Life 2: Episode 2.