Go to the room with the Dispatch sign above the doors and go to the subsequent room. On the right side there will be a note. Approach the computer, select the "Door Locks" option, and click on the locked rooms to unlock them. One of the rooms will not be unlocked immediately and it will require you to input the password. Get away from the computer, leave the room, and then get back to it. Click on the locked doors again, and the password should appear automatically. Afterwards, a number of additional rooms should be opened, together with the room of "Johan Ross", where a tablet and a note can be found.
After entering the Dive Room, putting the ARK on the platform and activating the mechanism, all will malfunction, naturally. You now have to find and open 3 pipes, which are used to pump water into the room. Two of them can be found to the left of the Omnitool panel, while the last one is located on the other side of the room. When you open all of them, a short cutscene will initiate. When you regain control, go through the open passageway, and then go straight ahead, pushing the junk aside. Some of the obstacles must be passed through by crouching.