The Xen teleporter brings Shepard back to Earth in front of an elevator that takes him down to an underwater complex of the Black Mesa facility. Upon entering the underwater facility, Shepard locates a trapped scientist that he frees after killing the nearby Pit Drones. Said scientist opens the locked door blocking Shepard's path, but he's unable to open the locked door to the following teleporter room due to an electrical current that could kill anyone that approaches the door. Shepard finds a way around through a Pit Drone infested vent to end up in the teleporter room, and uses said teleporter on himself to teleport into the nearby water.
Shepard swims his way to another part of the underwater facility where he has to open a hatch to the next area, but it also results in releasing the Ichthyosaur swimming in said hatch. Shepard bypasses the Ichthyosaur to the next area where he fights through several more Race X aliens until he reaches a portal that briefly takes him back to Xen. He then goes through another nearby teleporter on Xen that takes him back to a final section of the underwater facility. Shepard goes back into the water to bypass a couple more Ichthyosaurs in order to reach a sewer tunnel that leads to the next area.
This Chapter contains examples of:
- Shark Tunnel: This chapter, where a few of the lovely Ichthyosaurs have broken out of.
- Under the Sea: A lot of this level takes place within an underwater complex of the Black Mesa facility.
