Answer:
A hole leading in, a hole leading out, we connect to a cavern that is slimy all throughout. What are we?
To cross the water I'm the way, for water I'm above. I touch it not and, truth to say, I neither swim nor move.
What type of bar gets you wet walking in and out of it but keeps you dry inside?
We are all around, yet to us you are half blind. Sunlight makes us invisible, and difficult to find.
I am mother and father, but never birth or nurse. I'm rarely still, but I never wander.
What language does a billboard speak?