Courage Under Water (水の中の根性 Mizu no naka no konjo?) is the 140th chapter of the manga it is also the second and final chapter of the Akane's Swimming Lessons - Principal Kuno Arc. Akane and the Principal persevere with their swimming lessons. The Principal stays up all night sewing a swan training costume to help Akane learn how to swim, but it almost causes her to drown. The mermaid costume works just as well too. Akane is ready to call it quits when all her friends from school rally behind her and give her the encouragment she needs to continue on.