There are a few areas like this... But this is the worst of them. I had the pool replastered last summer and this happened right after and has not gotten any better. The water tests good and these dark streaks are very smooth to the touch. Sand paper, steel brush have no effect on this...??? I contacted my pool company at the end of the year last year and he agreed that it was not normal but said to wait until this year and he would come out when he could get in the water and try a couple things... Its not as noticeable when its really sunny but for that amount of money I don't feel like I should have to deal with ugly streaks in the pool??? Any advice?