I go up and I go down towards the sky and the ground

Question: I go up and I go down,
towards the sky and the ground.
I'm present and past tense too,
Let's go for a ride, me and you.

What am I?

Question: What fish only swims at night?

Question: What kind of mouse does not eat, drink or even walk?

Question: What has a bed that you can't sleep in?

Question: What tastes better than it smells?

Question: What goes in the water black and comes out red?