I was asked by the aweseome Peter Jensen Bissell on Twitter if I knew of a way to delete watermark presets. After doing some digging around in Lightroom 3, I found out that it is possible to do, but not the most straight forward option. Here's how to do it.
Go into Lightroom and hit "Lightroom" in the toolbar. Go down to "Edit Watermarks".
Now, go to the preset you would like to delete or change. For this example I want to delete my "pete" watermark. I don't use it that much.
Once the watermark is loaded up, you will see that you can adjust it and make changes to it and click "save". What you won't see is a delete button, which would be the easiest route. You will now need to go back up to where your preset name is and click it again. You will now see a few different options, including a delete preset option.
Click that little fella there and you no longer have that preset.
That's it. From there you can make another preset or just close out of the edit watermark menu. I haven't check it, but if anyone knows if the Lightroom 4 Beta has an easier way to do this, let me know.