Best Blue is a manga series written and illustrated by Masahiro Hirakata. It was first serialized in Weekly Shōnen Jump in the 32nd issue of 2015, on July 13th, and is currently ongoing.
Since that one day, the goal was to reach for the "legend"——
Aono is a boy on a rural island who swims alone, dreaming of the day to enter his own competition. He has no teammates, no coach, nor any rivals. Under this adverse environment a destined encounter awaits him?!