There are 4 secrets in this level.
Secret #1: Crawling into a wall
In the first room that is not underwater, with some kind of alien generator and 4 switches that require a combination, swim on the water surface towards the wall where the switches are located. There will be two pillars and the monitors and switches between them. Just crawl into a wall on the exterior side of either pillar, just above the water surface, you will find yourself inside a small corridor with 2 ammos for freezer, an armor and an atomic health.
Secret #2: Pillar with RPG
In the same room, insert the correct combination from the alien switches which is, counting from the left 1-0-1-1. The generator will lower on the center of the room, revealing a freezer weapon. Jump onto that generator - you will hear a door slam. Now jump towards the wall opposite of the monitors, where a vent is located. Turn around and you will notice the pillar behind you has opened when you touched the generator. Go inside and collect RPG. However, you have to be fast with this one as it will autoclose in a few seconds.
Secret #3: Blowing walls
When you enter the room with the waterfalls, head right and into a corridor with a ramp. Look on your left hand side and up - you will notice a crack on the wall. Use some explosive weapon to blow it up. Now head forward and turn left - you will be easily able to enter the hole you created from here as the ramp has lead you up. Inside you will find 2 boxes of pipebombs.
Secret #4: Getting cocky
This one might be risky to get. It is located in the room where the fight with Overlord takes place. First, you have to get inside the control room where the Overlord spawns at first. Then turn 180 degrees and run towards the opposite wall of the big room with green walls - a small place opened there. You have to visit it quite fast as the door are set to autoclose, but the steroids are not necessary. Inside you will find two boxes of rockets for RPG, ammo for devastator, portable medkit and an atomic health.
Achievements (Megaton Edition only) Edit
- This level contains an exit button that can be reached without using cheats. See the "Redundant Exit Buttons" section of the exit button page for more information.
- At the back of the room where the Overlord awaits, looking out the window reveals what appears to be a gun firing at earth. If the player uses dnclip and goes through the window, the player can be shrunk by shrink rays.
- This level presumably takes place on the "Titanic Alien Ship" that was mentioned after Duke defeated the Battlelord in the cut-scene at the end of The Abyss. When one looks out the window, however, the ship is nowhere near the moon.
- The fight with the Overlord in this level is referenced in the Duke Nukem Forever opening sequence.