While trying to obtain all the Mushrooms in the Swamp, I came across something while trying to go out of bounds. I came across this little thing, but it doesn't seem do anything, and it has no collision. Here's how to find it:

I'd recommend you have the upgrade that allows you to fly farther.

First you need to go to the Entrance to the Swamp. There you'll eventually come across this area.


Now what you need to to is to head closer to the barrels. This isn't the only way to get there, but I'm going to tell you the easiest. At the end of the path you'll find a few exturing roots.


Jump on one of these roots and hover over to the other side. There you'll find a gap in the barrels you can walk through. Behind the barrels are a few puddles, and in one of those puddles is the mystery object!