Stick to pools.
First of all, the ocean is deep as fuck.
So deep, we're actually not sure how deep it is, which is terrifying to think about.
Edited image via Emily Chack.
Source: i-am-bored.com
What we do know is that the pressure is so intense, no human* could make it even a quarter of the way down without THIS happening to his or her body:
*Unless you're James Cameron and you can afford to build a pressure-resistant robot to take you to the bottom of the ocean.
Source: fctn.tv
This is what most of the ocean looks like:
Pitch-frickin'-black. If you're afraid of the dark, I don't recommend going to the bottom of the ocean.
Source: raoulpop.com