system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: They say that 95% of the ocean remains unexplored. Why is that we can explore billions of miles into outta space but not a couple of miles down in the ocean?
gpt
Sea Pressure.

In outer space, it's essentially a vacuum. So the difference in pressure between the inside of the space shuttle and the outside is about 15 psid.

The deeper underwater you go, the stronger the sea pressure. Imagine a column of water. The water at the very bottom of that column is being squished by ALL the water on top of it. For every 100 ft of water, there's about 44 psi of pressure being applied.

So when you go down thousands of feet underwater, you have a LOT of water on top of you, trying to squish you. The underwater vessels can only be built to withstand a certain amount of pressure before they're crushed by the immense force of the water on top of them.