I haven't seen this film since 1964, except for excerpts on YouTube. My recollection is that it was the most beautiful film I had ever seen. That said, the other reviewer here (Martin Hafer) comments that the YouTube version is faded, which is either true, or my memory of the original is unclear...
I first want to comment on the summary at the top of this page: it's rubbish: "mostly filmed in deep-water seas from within a special designed batiscaff, by the Cousteau family of sea explorers." It was not filmed in deep water, it was filmed nearly entirely (see below for the exception) on a shallow coral reef in the Red Sea. There was not "batiscaff", nor yet any bathyscaphe. A bathyscaphe is a very deep water (abyssal or hadal) craft consisting of a steel sphere hanging from a large float, the float typically containing gasoline (because it's lighter than water). The Calypso's diving saucer, which is featured in this movie, is a small disk-shaped submarine capable of descending to about 1000 feet (300 meters). And finally, while Cousteau's wife is featured in the film, this is not a film about his family: most of the divers are not related to him at all.
Most of the action takes place at the Conshelf II station, 10 meters down, or the "Deep Cabin" at 30 meters. It was fascinating at the time to consider living underwater, and I dreamed of someday having such a house. For the most part that picture has not been realized in the way expected at the time (nor do I have my underwater house). Underwater "habitats" have been used by marine biologists, but many other things can be accomplished more easily in other ways.
The film becomes a bit hokey at times, as when Jacques Cousteau is standing in the ten meter house drawing a diagram of the two structures for his people. They obviously know all about it, and look suitably bored. (They're also smoking, which was typical back then.) There's another scene in which the diving saucer surfaces inside a cave that is both above and below water--but that was filmed in the Med, nowhere near Conshelf II, and was probably included because it was entrancing, and there was no other film to put it in.
But all in all, a gorgeous view of a future that could have, but didn't, happen.
