Just like the first series, Blue Planet II really made waves. The false killer whales and dolphins catching up on holiday every year, the barreleye fish with a transparent head (WHAT), the 'rockstar' octopus who made her own armour – it was all incredible viewing.
Sir David Attenborough and the BBC conveyed a very serious message though: we humans are doing massive damage to our seas and everything that lives in them. The BBC website has a useful page about the issues explored, and what you can do about it.
It's essential viewing, and re-viewing, and luckily you can watch the whole series on BBC iPlayer for another few weeks.
This is just the trailer, for crying out loud.