Amazing underwater photography as a South African documentary filmmaker follows a single wild octopus in the bay off his home for a year. Octopuses only live about a year, so he filmed about 80% of her lifespan. During this time she came to know him, became unafraid, and willingly interacted with him (including snuggling on his chest). He (apparently) filmed her hunting crabs, learning to drill into shells to disconnect the muscle at the back that holds the meaty bits inside, and her being attacked by a shark and losing a leg.
It grew back.
In the end she mated with a male, retreated with her egg sacs, and died when the young were hatched.
The apparent detail he was able to film -- I'm sceptical because Disney was famous for faking nature films -- was astounding. Lots of great underwater shots of him surrounded by fish, jellyfish, seals, an otter, and sharks.