The film that introduced me to the hydrosphere was The Big Blue by Luc Besson. Avatar 2 by James Cameron is a film that has used freediving techniques extensively. Actors were trained in advanced freediving techniques to be able to hold there breath for several minutes to be able to film all the required scenes. Without the use of freediving, this film would not have been what it is, I am grateful that James Cameron has chosen to use these breath-hold techniques and skills to create this masterpiece. It will come out in 2021 in 3D. I am really looking forward to seeing this sequel to Avatar when it comes out.