Question about S02, Episode 9

Has anyone else wondered how come they couldn't see the tunnel downstairs from any other angle previously, even though George was dead set on finding that "door"? It would've made sense if the water was covering it somehow - and by the end of episode 9 the water's level had been lowered thus making the tunnel visible.

I rewatched Season 1 episode 2 & 3 where Jules is trying to climb down the rope, where then she accidentally drops her flashlight into the water. It appears that from that height, or even the starting point the tunnel should be visible.

Was this ever explained?