system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why doesn't the ocean's water leak out the bottom and into the earth's crust/mantle? The ocean bottom can't be completely free of fissures, can it?

I was looking at the ocean the other day and wondering how it just contains all of its water.
gpt
* the water doesn't have anywhere to go.  There aren't gaping holes for stuff to fall into.  Any holes there are has stuff coming out (lava), not stuff going in.
* any water that does actually make it to a hole gets turned to steam pretty quickly (by the lava), and starts going right back up.
* rock is more dense than water.  That doesn't just mean that rocks sink in water, that means that water _floats_ on rocks.  The natural place that water wants to be in relation to a rock is above it, in the same way a beach ball wants to be above water.