Take care here, as the centerpiece of the setting is a pressure plate which triggers a very nasty (and noisy) trap that you don't want to attract the attention of further Falmer with. Leap it if you must, edge past it if you can, but whatever you do don't trigger it.
Then come to an immediate stop. The next cave is home to a Falmer Skulker, a magic-and-weapon wielder, and his pet small spider. Coming down from a hop over a trap is a terrible position to be in at the start of a fight, but if you wait a moment you can gather yourself before the Skulker comes into view. Kill him and his pet and you can gather the truly astounding array of alchemically useful fungi from this room.
Through the hole to the next cave you'll want to immediately look left- another spider is here, and behind it, another Skulker. What's more, there's a bend in the cave beyond which a second Skulker patrols atop a ledge- getting the attention of the first enemy archer will usually roust the second, forcing you to rush or take extra arrows to the face. Advance cautiously through the water as you go, for the terrain is uneven and you may find yourself caught on it if you try to back up while you fight. Once you've dealt with the two Falmer, head up the ledge and use it to cross the passageway- this gives you a shortcut to high ground for the next part of the cave, and gives you a chance to take out another sword-and-shield Falmer.
This one had his house up here, and some worktables besides, where you can grab up some Chaurus Chitin and iron ore. This is important, because the chitin from chaurus is the only item that you can use to improve Falmer weapons and armor. While the Falmer gear itself is mostly terrible, their bows are amazingly strong (likely to make up for the abysmal quality of their arrows, which you doubtlessly are using something far superior to at this point).
Scour the falmer hut and the rest of the area for still more fungus, then slip past it on the right and into a new passageway. This ends up on a long ledge that rises as it circles the edge of the cavern here, and the Falmer that guards this area paces up and down the ledge constantly. Jump him when he reaches the top and you might be able to take him out without attracting the attention of the two chaurus feeding in the shallow water below.
If you're cautious about it, you can even kill the chaurus from here- they're locked into their area, so you only have to worry about their spitting attack taking you down from up here. Be cautious though, as more falmer wait further into the cave and ou may wind up accidentally alerting them to your presence.
Once the chaurus are dead, carefully follow the ledge down to the cave floor- you'll come up behind a falmer standing in front of his home, a convenient thing for a pickpocket. Be careful, though- across the cave and up on a ledge, another one repeatedly emerges from his home to pace, and this one is an archer. A third falmer waits out of sight to come charging around the bend at you as well, if you make yourself known.
