MOLES!
Those gosh-darned moles. Not only do they dig up the yard and turn it into an ankle break waiting to happen, they are digging UNDER the swimming pool. What does this mean? When the tunnels collapse, we get a wiggly little trench in the bottom of the pool. Do you have any idea how much a pain in the butt it is to brush and vacuum those little squiggly trenches?? Do you? Ugh.

