How deep is the ocean?

You're standing at the beach, toes in the sand, looking out at all that water. It goes on forever, blue meeting sky at the horizon. But how deep does it go DOWN? If you could walk straight down from here, step after step into the dark — how far would you walk before you hit bottom?
The ocean isn't one flat depth everywhere. It's more like a giant bathtub with hills and valleys underneath. Near the shore where you're standing, it might only go down a hundred feet — shallow enough that sunlight reaches the sandy bottom and you can see fish darting around. But walk out further, past where the waves break, and the floor starts to drop away.
