Blue Planet III review: David Attenborough delivers marine marvels in this thrilling sea-quel

Cast your mind back to 2017. There were big beasts in the schedules back then: dramas like Broadchurch, Sherlock and Line of Duty; reality shows like Britain’s Got Talent and The X Factor. So what do you think was the most watched programme of 2017?

It was of course Blue Planet II, the BBC’s belated sea-quel to 2001’s The Blue Planet. The opening episode was watched by 14 million people. In the end-of-year top 10, episodes of Blue Planet II occupied the top four slots.

Viewed from 2026 (barring The Celebrity Traitors and... The Traitors) those figures look astounding. They may be one reason the BBC has ordered another helping, a threequel to give Sunday nights a boost in an era when linear TV ratings sometimes look as if they’re heading for Davy Jones’s locker.

Hence, we now have Blue Planet III, with David Attenborough narrating again, his oaken voice weathered by the years, alongside an A-list underwater cast. Top billing in episode one goes to a pair of Indonesian harlequin shrimps – flashy, frilly characters who have clearly been at the dressing-up box.

It turns out they’re tough as old boots when it comes to taking on a starfish many times their size, and their MO is enjoyably macabre. It’s one of several scenes in the series with a hallucinatory edge, the sense that we’ve entered a nearby parallel reality – which is exactly what you want from a nature show.

We get to enjoy the suave enormity of a blue whale cruising by. There are moonlit baby turtles nosing out of the sand on a Mexican beach. We see dazzling mahi-mahi fish that somehow change colour as they move in to attack a giant school of sardines. And the trippy synchronised swimming of the sardines themselves is fabulous – a silvery swirl moving like a high-end screensaver.

But hang on, doesn’t some of that sound familiar? Yes, to be fair, we have seen some of it before. There have been sequences on sardine bait balls in previous nature series, and turtle hatchlings, too, though Blue Planet III does its best to up the ante. Also, if we’re being really picky, a pair of harlequin shrimp featured in The Blue Planet, 25 years ago.

But if wildlife series, like comedians, sometimes rely on old routines, that’s broadly fine as long as there’s also eye-catching animal behaviour that we haven’t witnessed before, the natural-history equivalent of a world exclusive.

There are several in the first episode, including sharks that hunt as a team, or as close to a team as sharks ever get. And there’s a pregnant dolphin who appears capable of planning, problem solving and tool use – skills that some men I know haven’t mastered yet. We see her plucking up tufts of sea sponge, then jamming them into gaps in the coral where fish will otherwise escape her.

By the time we reach episode three, the wonders come thick and fast. I have never seen anything quite like the colony of 200 million porcelain crabs in the seas off Chile – just extraordinary. Then there’s a great scene where a Japanese octopus leaves the seawater to hunt food in the open air, writhing awkwardly across the rocks, legs all over the place. And at one point, a whale in Patagonia just looks at us with her big, barnacled eye and then we hear her give her mating call, like a huge, sexy foghorn.

The trouble is, watching these marine marvels, we always know that at some point there will be a needle-scratch when the spell is broken. That’s how nature series work: they have to acknowledge habitat loss and climate change, or it feels like cheating.

In episode one, the reality check arrives at a cruel moment. Just as we’re cooing over a Pixar-pretty clownfish, we see the sea anemone where it lives turn white because a heatwave has caused bleaching. Countless reefs have bleached and died in recent years, Attenborough tells us.

He does so in the voice of a weary sage who has seen it all, has visited every wonder on the land and in the sea. He has been telling us for a long time that the natural world is precious, that most of it is water and that we should take better care of it. By now he may feel that we watch but don’t listen.

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Blue Planet III airs on Sunday 1 November at 8pm on BBC One and iPlayer.

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