It's really dark down here, that's me and Emily, we are already standing in water. Here's a video of us sloshing through the tunnel. The part you see, the water is not very deep. When we first got in, it was several inches above my knees. Felt cold at first, but we quickly got used to it. This is fresh water that is always flowing from the Gihon Spring, which is in the City of David, the same spring all the people got their water from around 1000 BC.