As you wander through the Hadal Blacksite, you reach door 80. It's a big room, with big windows for sure. You look outside the window, water and green lights to guide you through, maybe. You go downstairs, in some sort of airlock. You begin to hear HQ's voice, listening intently.

"The quickest way ahead is to exit the Blacksite. Enter the airlock, pull the lever, and swim to the other side. Do not stray too far from the beacon's path, as the fauna in the trench prefers the abyss. Please keep in mind that Leon is about to pass through the area. Please be careful of his steps. He is quite unpredictable."