I want to add the unfair reviews earlier in this thread from some who "haven't even watched it" are a little silly.
Documenting history should be based on facts, not a producer creating and twisting the narrative. Which didn't happen here. In fact, I appreciated the fact there was not a narrator. The story is told directly from the divers themselves.
Also, criticizing the way they were diving back then is also unfair. They were doing cutting edge diving and we all know generally speaking those before us who took on these challenges and pushed the limits pioneered and created the training and education we appreciate today. I equate the criticism to calling the first space missions dangerous and careless because they didn't adhere to the same safety procedures and equipment used today.
If you're on the fence on buying and watching this film because of the earlier reviews, do it. You won't be disappointed.