Removing a watermark is not easy, they are there for a reason, to brand the image.  

In fact, you can easily add watermarks to your photo's with Lunapic.com's Watermark tool. 

However, if you want to remove a watermark, there are a few ways of doing it, you may want to

view our video tutorial on removing objects from photos.   It uses a few techniques, such as 

remove and inpaint or copy and pasting other parts of the image over it.    If it's on the 

bottom or side of the image, you may just be able to Crop the image