I watched this on Netflix last night. If the octopus was the teacher, the student should have been failed.
The documentary is beautifully shot (after the unnecessary first part about his midlife crisis) and we see some amazing footage of the octopus, but my main takeaway is how selfish this man is.
He built a bond with her that was entirely one-sided. He didn't help her out with food while she was pregnant, and didn't save her from a shark attack (small sharks) either during or afterward because it would be "interfering with nature's process", but he had spent months with her every day interfering with nature's process. Frightening her, then gaining her trust, encouraging her to leave her den every day and gain confidence being out in the open and around him. Maybe she even saw this big friendly creature as a protector? Without his input she might have stayed carefully hidden and camouflaged as she was when he first encountered her, and not been attacked by a predator.
So the lesson is, we must not interfere with nature. Except for when it personally benefits us.