Not sure if this is just appearing like this because we are near water, but it seems that it does it when your background is over the water.
Hopefully it can get fixed ASAP because that is a horrible looking block in hand.
Also, could not find a similar " bug " in the quick search.
http://gyazo.com/368655bdfa2a5a242193af0aa2750a97.png
http://gyazo.com/76796fe3b2339b6b2906bbf20aae7014.png
Found the " issue " in Quick Search after some time, so this is a duplicate please close.