The first thing that comes in mind when I think about Japan and Sea is the great painting of Katsushika Hokusai. Yes , The Great Wave off Kanagawa.
That image shows the deep relation of this country to the sea and summer is the best time to enjoy the seaside activities and fun. Coincidentally this image was taken at Enoshima, Kanagawa. Just in that famous painting boats were tactically crossing the huge wave , this surfer too riding on that huge wave and brilliantly overcome it and came to the shore.