Electrical-Running UFB wire

[muddywings]

I'm going to run an electrical line to the back yard so the wife can have a nice fountain for the birdies.
I have a single circuit that runs to outside lamp posts that is accessed through the unfinished basement that I'm going to use.
Plan is to put on a GFCI on that line then run UF-B wire to the back yard, put in a weather proof electrical box and poof, done!
Now that have the trench dug up, I went to Home Depot to grab supplies. I talked with a worker who gave me some info on doing it and I'm kinda wondering how much of it is bs.
My plan was to run the UF-B wire right from the GFCI box, out through an ell/junction box, down 12" and buried per this website:
http://www.familyhandyman.com/electr...view-all#step1
The Home Depot rep said at the junction box, I had to de-sheath the UFB wire, and connect into normal NM (indoor wire) also de-sheathed, until it exits the PVC pipe inside the house. This seems kinda derpy to me.

Any advice?


ETA: for those wondering why I'm going through the trouble for a fountain, I already have the trench dug for a sprinkler line for a garden back there. Figured it would look cleaner than an extension cord running along the side of the fence.