Ningen (1962)

This is one of the first Japanese films distributed by ATG, preceded only by Teshigahara's Pitfall (おとし穴). Based on Nogami Yaeko's 1922 novel The Neptune (海神丸), which was in turn loosely based on real life events. It is the story of the ship Kaijin Maru, that is left adrift after losing all means of navigation in a storm, and the four people on it, becoming increasingly desperate as food and water run out.
#6 in Kinema Junpo's listing for 1962. Starring Shindo regulars Tonoyama Taiji, Otowa Nobuko and Sato Kei, and scored by the wonderful Hayashi Hikaru.