The Sumida Boathouse was not an existing boathouse. It was constructed especially for the film. The shack in the middle of the lake was also constructed for the film.
Unusual for a Sion Sono directed film, the actors were encouraged to ad lib and rearrange blocking.
The original comic of "Himizu" did not have any elements of the earthquake disaster of March 11th 2011. A script was already written in early 2011, but the director decided to add the earthquake disaster into the story, making it the first film released that directly dealt with the subject.
Director Sion Sono originally planned to make a straight movie adaptation of Minoru Furuya's manga, but following the Tohoku earthquake & tsunami adapted the story to fit into the post-Tohouku earthquake & tsunami Japan.
Movie is based on Minoru Furuya's manga "Himizu" (2001-2002, Young Magazine, Kodansha).