The Missing Water Bowl, Continued

Last month I wrote about the day that my two crafty basenjis hid their water bowl in the backyard while I was out a work (http://basenjirescue.blogspot.com/2013/02/the-case-of-missing-water-bowl.html).  While they haven't been crafty enough since then to completely hide their bowl from me (and I have the benefit of knowing their hiding places now... heh heh heh), since that first time, they've been bringing their water bowl out into the backyard EVERY SINGLE DAY! 

Every day now when I come home from work, I find a huge puddle of water on the kitchen floor -which is single-sheet vinyl, thankfully, so it doesn't seep through- and no water bowl where it should be.  It used to sometimes be elsewhere in the house, but not anymore.  It seems that my two mischievous pups have discovered that they quite enjoy bringing their bowl outside, and every day I find it partially hidden in one or another corner of the backyard. 

The thing is, I just can't figure out why on earth they do this.  I know that they're bored during these cold winter days, when there's not much going on outside and not much sunshine to lay in.  They've also gotten more destructive in the house (as my two recently shredded living room curtains can attest), which unfortunately has led me to have to gate off areas of the house that were previously open to the pups during the day.  But even still, boredom doesn't necessarily lead one to need to drag a heavy ceramic water bowl outside and hide it in a corner of the yard every day, does it??? Maybe in dog logic this makes sense, but I just can't figure it out.  Does anyone have dogs that also do this, or know why they would?  I'm completely flabbergasted here.