You were walking through the Hadal Blacksite, but when you hit door 80, some sort of big room appeared. You went to the window, revealing a bunch of water... But there was Blueish lights out there illuminating the ocean floor. You went downstairs, to the airlock. And HQ speaks.

"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 note: Rose is about to walk through this section. Mind the smell of flowers and swim carefully."

And that's what you did, you switched the lever, the gate to the trench opens. You put your mask on, protecting your face from the water. You swim into the trench, following the green lights. You look up... A big.. looking machine is just very slowly walking towards your way, it seems to be it has no eyes, just being controlled or something.. But you're not sure if it's being controlled or not. You make out it's appearance, blue holes on its feet illuminating the ocean floor, whatever. You just continue through the trench getting to the other side.