- Open the dive tank.
- Access the top floor.
- Blow the way out.
Possible secrets: 3
Cheat/s unlocked: Tiny head Duke (find all secrets)
Head down the corridor and nab Combat shotgun. Bust open the door next to 'Dive tank' sign. In next room you will see a big fishbowl (read: dive tank) as well as 1x PigCorps and 1x MiniMonkeyCorps. Head right and open another door for Combat shotgun ammo. Go back to fishbowl room and open the last door. This next area is pretty big and it has following enemies: 2x GorillaCorps, 4x PigCorps (2 of which are hidden behind a breakable wall and they will try to ambush you when you pass by). Some parts of this area have been blown away and small fires are burning in such places. Be careful not to dawdle in fire for too long. One of PigCorps in this area will drop Armor item. You can also collect Dynamite and Handgun ammo in this area. Now head past the two elevator doors. There are two doors in the small corridor you're in right now. Bust open the right door and press 'Elevator override' switch.
SECRET 2A: Go back to elevator doors. Left elevator is now open. Drop inside to collect Duke's biography item.
Go back in the corridor and go further. You will arrive into the room with pool on the left and big fan on the right. Kill 1x RoachCorps and 1x GorillaCorps in this room. Go to where GorillaCorps was and press red button which will cause the fan to start moving.
SECRET 2B: Press red button. This will stop the fan, but its position will be different now. Go behind the fan, destroy the grating and enter secret room containing Quest item. Go back to fan switch and press it yet again.
With fan moving you can now jump over the pool. Should you fall into the water, you can get out by climbing a small ledge found on fan's side of the pool. When over the pool, enter the door on left. In this room press 'Dive tank override' switch. O1 complete!
Open another room in this room. Now take right turns all the time until you land in 'Zero-G Test area' room. Kill 2x PigCorps and 1x MiniMonkeyCorps found inside. Press red button two times so that strange device changes sides (third yellow box should be blinking). Collect Handgun ammo left from red button. Now when device stops, climb onto it. Climb onto the vents until you reach 'Opening dive tank doors'. Destroy the grating, but don't jump in the pool yet. Across the room you will see another weapon. With few jumps you will nab Energy weapon. Climb back up to 'Opening dive tank doors' sign and jump into the fishbowl. Destroy the grating on the bottom and swim thru it. Bubbles you see here help restore your O2 gauge. Kill 1x RoachCorps. Follow your nose (get Duke's biography item on the way) and you will get out in restroom. Re-entry point and O2 complete!
Third restroom door has 1x PigCorps inside. When killed, he'll drop Combat shotgun ammo. Exit the restroom. Now you're in rather big set of hallways. For starters I suggest killing everything that isn't behind any doors and that is: 1x MiniMonkeyCorps, 2x PigCorps (one will drop Combat shotgun ammo), 3x GorillaCorps. At the end of hallway there are 2 elevators. To the left is a door. Open it, kill 1x GorillaCorps and collect Detonator item it drops. Now backtrack, but be careful. As soon as you enter hallway, wall on your right will crumble. Opening contains 1x PigCorps and 1x GorillaCorps. Another 1x PigCorps will come running down the hallway. Kill 'em all. Now it's a good time to check the rest of the doors. Opposite to crumbled wall is a door leading to Handgun ammo. Next door you come across contains 1x GorillaCorps. Exit and open next door. Inside collect Handgun ammo. Destroy fire barrels in the corner and collect Flamethrower. There's a showing room ahead with Laser blaster lying on the table.
SECRET 2C: Shoot the barrels to reveal secret area with Combat shotgun ammo.
The other two doors found in this two connected rooms lead back outside to big hallway. Two doors in the big hallway remain. One leads to a machinery room of sorts with nothing inside. The last door leads to another restroom with 1x GorillaCorps and 1x PigCorps inside (will drop Armor item when killed). Now go to where a dead Babe is (blue light shining from the ceiling). Use Detonator item on the bomb. O3 complete!