The Water Repellant Tang Wulin

The Asiatic Apple Douluo hesitated for a moment before she said, "Although you won't be fighting against the War Gods in the final three levels of the tests, I must warn you that this is the most difficult part of the test. As a War God, I can't tell you about the test. I'm only allowed to wait here after bringing all of you to this point. This is the War God Hall's rule."

As soon as those words were uttered, the whole group was startled. 

Shi Mengshan did not reveal anything, but she was actually warning them that the underground river was dangerous. Moreover, she insinuated that it would be a threat to them. 

It was because she knew their capabilities. Nevertheless, she still chose to warn them under such circumstances. Otherwise, their safety would be compromised.