This is a very large level, with some interesting secrets and multiple paths through it. It also probably sets the record for sheer liquid volume, emphasizing the size of the spaces Marathon 2 is now capable of.
Once you dive into the slime, there are two ways out of it: To the west and to the east. The east end also contains a 2x health charger and the place at which you will get the fusion pistol if you hadn't found the secret on Slings and Arrows, so we'll go this way. You can also get out of the slime much quicker here; if you did much exploring on the previous level you'll need oxygen.
This side of the structure contains the main terminal, whose first message is easy to miss if you took the other path into the level. And it's an important one: Tycho is alive, and very near. Also around here is an oxygen charger and a large, convoluted area which we will save until later.
There's a small bug when you activate the nicely built bridge leading across the slime: A ceiling light gets swallowed up by its underside. However, I can't see a single reason why you would want to cross this bridge! The other side is empty, which is not what I remembered, but whatever.
Back on the upper level, head west and take out the guards on the other side; this is also the point at which the two paths into the facility converge. At the large doors, take a moment to ponder the mysterious "i was left behind" terminal. Then head back across to read the hilarious story of the naked airlock technicians and beam out to Ex Cathedra.
There are two notable secrets on this level. First, there is the raised ledge stuffed with shotgun shells; it appears that this can only be reached by grenade hopping or a rather spectacular Vidmaster technique in which you are blasted out of the water by a Compiler. Second, there is the area we passed over before. Head back there and clear it out, picking up all the ammo as you go, then take a gander at the small room behing barred windows. In this room are 3 switches, shoot them all with the fusion pistol. The large bolts sometimes have trouble getting through the bars, be prepared to waste some ammo. Also, be very careful not to shoot the breakable panels right next to each switch, they will break the secret permanently. Once all that's done, head back to the 2x health charger (the one under the slime, not the one nearby) and look for the new hole in the wall, which leads down a LONG pipe and into the secret room seen earlier. Get on the rising platform, use it to jump to the stationary one, and then shoot the switches high up on the wall to make it go. This will take you to the roof, where you will find piles of ammo.
