A watermark is something someone puts on the inside of a skin that says they made it. You can't see the watermark from the outside and it's only visible with certain editors. So if you were to look inside this skin this is what you'd see this: http://gyazo.com/bc9929ff8fa45efa16eb26cf3ef84f7d

And then this is the inside of agapl's Sugarbun skin: http://gyazo.com/675b4c48882f6472b33a9f5cb5269c74

Now I'm obviously not saying you stole this skin as the two are nothing alike, I just found it odd this skin has agapl's watermark.