‘Horizon - How to Film the Impossible’:-
https://vimeo.com/54710740 - at the Jrmtrinquet vimeo channel. (A 1985 documentary - 50 mins)
Honestly one of these best effects-focused documentaries I’ve seen. I feel like a lot of similar documentaries tend to simplify things to much, but here they really take you through the process.
The remastered version by Harmy is really great, especially since most online versions tend to vary greatly in quality and never seem to stay long either before Horizon takes it down;
https://docs.google.com/document/d/1hQ0GQjmIWDPOv0Xs3rJ2SgzOLDVQoiP2gPeHBNuqZto/edit