For this you need a Minimum of 12500 points, to buy the necessary doors around the map.
Once all the subsequent doors have been opened, make your way to the
Poop Deck and use the travel pad that will take you to the
Forecastle, once at the Forecastle use the travel pad there to go back to the
Poop Deck.
When back at the
Poop Deck make your way to the Mid Deck part of the map, use the travel pad in the Mid Deck and you will be brought to the
Engine Room turn around under the water and make your way to the
Boiler Room which is where the next travel pad is located.
Go through the travel pad in the Boiler Room and you will be brought to the
Grand Staircase run forward to the area
Millionaire Suites and go through the travel pad.
Once on the other side you'll go to an area called
Provisions. Once inside the Provisions area go forward to the
Engine Room and go up the stairs on the left side of the room, and the next travel pad will be on your right.
Go through the travel pad near the top of the stairs and you'll go to the area called the
Boat Deck. Run from the Boat Deck back to the
Forecastle (Spawn area) to get to the
Cargo area. Go through the travel pad in the Cargo area it is directly in front of you under the water.
Now you will be teleported back to the Boiler Room, from here leave the Boiler Room and go across the Engine Room and you will see another door on the opposite side called the
Turbine Room.
Go through the travel pad inside the Turbine Room which is under water and you'll be teleported back to the Cargo area, and you will get the achievement.
Call of Duty: Black Ops 4 I Know a Shortcut GuideI hope this helped, thanks again.