It's not a pool, it's an image error (it's covering the tops of the trees)
Blue Circle Image Error
No Thumbnail
© Bing Maps
By SpiderX22 @ 2014-04-14 18:34:02
SpiderX22
@ 2014-04-14 18:34:54
Please add to scavenger category "Error in satellite imagery other than a lens flare"! I misclicked the category and it went away