The David Attenborough series has also been occasionally heartbreaking. The third episode — titled 'Big Blue' — featured one moment that left people in tears.
"This mother has been carrying her newborn around,” said Attenborough, narrating over a family of pilot whales, “but it's dead. She's reluctant to let it go. It’s been dead for many days.”
Attenborough explained how humans dump around eight million tonnes of plastic in the ocean every year. As a result, the water levels had likely become so toxic the mother’s own milk had been contaminated
"Pilot whales have big brains, and they can certainly experience emotions,” the narrator continued. “Judging the adults, the loss of the infant has affected the entire family.”
Following the scenes, some viewers took to Twitter to express their dismay at humanity, calling on others to do something about our poisoned oceans.
#blueplanet is making me sad. We truly are the worst dickheads on the planet— Nooruddean (@BeardedGenius) 19 November 2017
Blue Planet is just: look at this amazing stuff! Do you like it? It’s great, right? WELL IT’S DEAD.— Hayley Campbell (@hayleycampbell) 19 November 2017
Spotted that each episode of this series of #BluePlanet has about 45 mins of how amazing the wildlife in the oceans is and then 5 minutes on how we’re needlessly destroying them— David Swanson (@DJSwanson13) 19 November 2017
I found tonight’s Blue Planet mesmerising yet terribly sad. The images of dead coral reefs made my heart sink.— fearne cotton (@Fearnecotton) 12 November 2017
Its actually quite depressing watching Blue Planet 2.— World_of_Stu (@stu_the) 12 November 2017
The world is in amazing and beautiful place and its with a heavy heart that you realise that we are the cause of everything that's wrong with the Earth. #BluePlanet2
Very impressed that #BluePlanet2 tackled the terrible issue of bioaccumulation of pollution from plastic in large predators. Truly heartbreaking.— Plastic Free Pledge (@plastic_pledge) 19 November 2017
Blue Planet has issued an article explaining what can be done to help preserve the sea, the first piece of advice — and quickest for those who live by the sea — being to simply pick up litter at the beach. They even call on those who do take part to Instagram and Tweet #2MinuteBeachClean.
Another tip is eating sustainably caught fish — which ensures wildlife and habitats aren’t affected by fishing. The Marine Conservation Society has a handy guide for finding out whether what you’re eating is sustainable.
For those watching Blue Planet II, you’ll be happy to know every piece of plastic the crew came across was removed from the ocean and recycled.
"There would rarely be a dive where I wouldn't find some form of plastic from a thread of plastic fishing line, sweet wrappers or plastic bottles," assistant producer Sarah Conner told BBC Newsbeat.
"When in the open ocean on the boat, if we noticed rubbish while in transit we would do our best to stop and pick it up, just as anyone who cares for the ocean would hopefully do."