|Click the frame above to see the movie. Or, option-click (right-click on a PC) on this link to download it directly to your hard drive.
To get beneath the LightBridge in the cave, you need to drive the Warthog off the edge of the second platform, and land on the far wall, which has a steep slant to it.
You must give the Warthog a little spin as you leave the edge of the platform so you'll hit the wall facing up. This is the key to making this trick work. To do this, start a turn just as you approach the edge. Use the second joystick, which controls the "camera" view when the Warthog is airborn, to watch the Warthog fall and spin towards the far wall.
When you hit the wall, hopefully you'll still be in the Warthog, and it will be facing up the wall. You may bounce some, but just try to steer the Warthog so it faces up. Use the accelerator to slow your descent as you slide down backwards. Soon, you will reach the floor, and you can back onto it gently.
There you have it. There's not much down there.
Although, the view from below, and the dark silouettes of the Warthog and the gun-toting Marines, blanketed in the haze, are kinda cool for screen shots.
Enjoy the purple haze.