The inherent conflict of being alive is that your cells just love water. Great stuff for cells. Excellent for transporting things around in, really helps counteract gravity and make that 3rd dimension fully accessible. You as an organism however, want atmosphere. It's got all those awesome gases, like oxygen. Those gases are great! But they're not very good at getting in the water. Lots more of them outside the water.
Now some organisms went ahead and said "well, our cells want to be in the water, we're made of cells, we're staying in the water". And I respect that! Gotta respect that. Lots of 'em stick to the surface, get a little bit of the good gases, but keep themselves nice and watered up (wet) to keep their cells happy. Some make do with whatever cool gases have managed to dissolve into the water, thanks to a process known as "churning that shit up" that happens on the water's surface. Doesn't work out great for them, but you know, they made their decision and they committed to it. You gotta respect that.
Now some organisms, especially a lot of old ones, were afraid of commitment. They hung out at the water's edge, breathing all the gases and shit, but still needed to make sure they could stay wet. Like, their plan was to leave the water, but stay wet. Not a great move, if you ask me. Usually it works, but only until it doesn't. You ever seen dried up moss? Ask it how it's "stay wet but not in water" plan went. It can't answer you. It fucked up. That's what you get for not committing.
Now trees though, trees had the other idea. Trees and some other plants were like, no problem. I'm gonna take my water with me and never ever let it go. They developed specialized cells and shit. They got whole layers dedicated to keeping the water the fuck in. They got other cells dedicated to hunting down any water in a square fuckometer and taking it for themselves. That's hustle. That's a game plan. Some plants got so good at it they saw these dry-ass stretches of land that saw rain less often than you saw your mother smile as a child and were like "okay but is the amount of water not literally zero? Yeah? We're good."
The moving orgisms tried to copy trees, naturally. Making hard outer layers to trap the water in for their cells. But it was pretty weak. They kept going on about needing holes for the moisture to leave, and wet surfaces for their eyeballs. Then some of us got stupid and decided maybe we only needed like a half-decent layer protecting our water. "Semi-permeable" they marketed it as. Oh it's fine they said. We'll live somewhere wet, they said. Yeah how'd that work out for that moss again.
And now I get a headache if I go like 3 hours without drinking a glass of water. I should've been a pine tree.
