You continue on past the rats, tossing the third's body into the water as you pass. The reeking smell of the sewer is getting stronger, and you come on to another fast flowing tunnel. Your only option is to turn right, and you do so, following the tunnel another hundred yards or so.
At this point, there is an eerie, greenish-silver light glowing from the water, and the walls are painted in places with gibberish words in the common and dwarvish alphabets. Nothing actually spells what might be a word- there are too many consonants and vowels in rapid succession, and even some numbers and nonsense symbols. The rats are quite thick on the other side of the water here- instead of every hundred feet or so, seeing a clump of them, you see dozens at a time, running about and peering at you with their beady eyes.
The tunnel starts sloping downwards, and at this point, the tunnel breaks away from the edge of the water, heading downwards at a 30 degree angle diagonally away from the water, which continues along behind a wall.
I presume you continue, and thus, after walking down this grade, you come to a large, iron door. There are several symbols drawn on the door in a red chalk, and there is a line which appears to be made of salt drawn at the base of the door. The door is etched with words: "Lower Level".