What is it?

When I walk through the forest, I see fallen leaves, bent trees and flying bees.
I wander in deeper, things linger below,
Some as thick as a finger some nearly hollow.
They crawl everywhere even on my body, for a fact!
I stood still and I saw one, fairly fat!
It lumped around sharp and round. It picked my skin! And made a very bad sound!
I saw some roots!
And some very nice fruits!
Some were berries, some were cherries,
But my favourite of all was something very tall.
It looked like a mouse, as big as a house,
It is found in the sea.
It's sort of like a tree, but it has eyes like me!
It's dark blue and can give you the flu!
It's like grass all soft and floppy but what it really is… it sounds very poppy!
It gives you a shiver almost like a critter!
It gives you a headache like the sound of an earthquake!
It's like a denture but much more in the centre!
It reminds me of nature and it really is something major!