system
Given the following post, respond as if you're commenting on Reddit:
human
eli5: why does the sea not sink through the sand?

Or how deep do you have to dig on the bottom of the ocean before you reach dry sand?
gpt
You get sand when water (or wind, but that isn't relevant here) whips rock into pieces. Under the sand, where water hasn't been able to whip it out of shape, is just rock. Water doesn't quite seep through rock.