The TV series built a world so strange and beautiful that people needed more time inside it. These specials don't explain what you missed or tie up loose ends. They just let you stay with the Mud Whale a little longer, watching the people in it live in the quiet moments between the plot. That's enough. For a show this atmospheric, atmosphere is the point.
Two special episodes accompany the home video release of the Children of the Whales TV anime. They were included with the Blu-ray and DVD volumes, and both take place in a school. The specials carry the same Drama, Fantasy, Mystery and Sci-Fi genre labels as the show they supplement.