This chapter of the Metro Exodus Sam's Story guide describes the next part of the game, where you have to find a diving suit.
Go to the marker on the map. Climb up the wooden ladder to reach the top of the building and then enter through the window. Collect items and move on - the path is very linear; you shouldn't have problems with reaching the goal. You finally reach the bandits - kill them.
Go outside and defeat more enemies. After a while, you will reach the boat - go up and use the lever to open the passage. Then go back to the boat and move forward. You quickly get to the hangar - further use of the boat will be impossible. Go to the hangar and continue on foot.
Walk on the pipe and shoot the tentacles. Go up the ladder and move on and then interact with the handle. Use the box next to you to light everything beneath you.
Return to the boat and continue swimming until you reach the pier. Go to the marker and you will quickly encounter enemies. Kill them and enter the large building. Get to the staircase and go up. Defeat more enemies and dogs. You finally reach the room where Sam can wear a diving suit and pick up the equipment.
Go to the top, climb the stairs to the top, and then use the rope to get out of the building.