"They are, as you stated, watertight. In reality, you could achieve the same results with a foodsaver, or even just putting them in tiny ziplock bags...but it was a lazy Sunday afternoon, and I had been thinking about doing this...and for some reason I thought I would share my work of art with the backpacking community ;)"
Not to mention brag about the cool tools you have access to, eh? ;)
And, yes, I'm jealous. :D