The Red Pill, the Youtube Red documentary, is likely the best documentary I've seen. It's funny to me how many people will refuse to see it, but I watched it, and found not only that it was interesting and informative, but it also shed light on things and changed my mind on things in a way that persisted in the face of subsequent scrutiny and research. It's really really good and I can't recommend it highly enough.
There's also a documentary about a guy living on the edge of the ocean, I think it was in South Africa? He goes diving to reinvigorate his love for life, basically, and documents a large portion of the life cycle of an octopus. Visually it's compelling, and go figure, I'm a sucker for octopodes, so I am a big fan of that one as well. I think it's "My Octopus Teacher". However, it might be because I'm a sucker for a poignant score and octopodes but I found it to be a very emotional watch, just as a forewarning.