In this episode of the History Slam, Sean Graham talks with filmmakers Nate Slaco and Bryce Zimmerman about their new documentary Moonless Oasis, which profiles efforts to study and preserve the remarkable glass sponge reef in Howe Sound north of Vancouver. They talk about the glass sponge reef, the challenges of shooting underwater, and importance of capturing the reef on film. They also discuss the efforts to preserve the reef, whether this is a nature or human story, and why the reef is an important national story.