The next installment of the Emmy-winning “Planet Earth” franchise, “Blue Planet II,” focuses on the ocean, and it doesn’t disappoint. Sir David Attenborough returns to narrate extraordinary footage of sea life, much of which has been filmed for the first time. It is a visually stunning series that will surprise and delight you.

Production was a monumental undertaking. The series was filmed for more than four years on every continent and across every ocean with a creative team that visited 39 countries and spent over 6,000 hours diving and filming. Technological advances including ultra-high definition low-light cameras and submersibles that allowed producers to be the first humans to dive 3,280 feet into Antarctic waters, produced exceptional footage of behaviors and creatures never before seen.

Revealing an ocean world full of compelling animal characters, each episode is structured as several stories that are expertly connected through Attenborough’s narration and a soundtrack that seamlessly moves from tense drama to whimsy. In one story, there is a Giant Trevally fish that leaps out of the waters of the Indian Ocean to catch seabirds called Terns, in mid-flight. When Attenborough gives the baby birds human characteristics by calling them “youngsters,” and the high-speed footage captures their battle to survive the hungry mouths of the Trevally in slow-motion, it’s a moment full of suspense. Will the youngsters make it?

The music reaches a crescendo, one particular seabird somehow escapes and the Giant Trevally crashes to the sea without its prey. I’m pretty sure I gasped at this point.

In another segment, which is my favorite from episode one, we meet the Tuskfish, an orange-dotted fish that swims in the waters off Lizard Island, Australia. Every day, the Tuskfish travels to the outer edge of the reef, uses its sharp, protruding teeth to pick up a bivalve and takes it back to a formation of coral shaped like a bowl. In this coral kitchen, the Tuskfish will fling the clam repeatedly against the rock to break it open. As Attenborough charmingly quips, “Some fish are much cleverer than you might suppose.” Indeed.

There are surfing dolphins in South Africa, Mobula Rays putting on a bioluminescence light show in Mexico’s Sea of Cortez, Orca and Humpback whales feasting on herring in Norway and gender-changing Kobudai fish in Japan. Every story segment is beautifully produced to create a sense of wonder and awe.

As much as “Blue Planet II” is inspiring, it’s also a lesson that our ocean system is changing. In a segment on Walruses in the polar north, we learn that the summer sea ice has retreated by forty percent in the last 30 years, with serious consequences. Attenborough’s narration follows a female Walrus and her pup as they search for a patch of ice that will keep them safe from predators. It’s a drama filled journey, made more so by Attenborough’s use of anthropomorphism, but the message is clear. How many more seasons until there is no ice left on which to rest?

“Planet Earth: Blue Planet II” premieres on Saturday, Jan. 20 at 9 p.m. EDT, simulcast on BBC America, AMC, IFC, WE TV and Sundance TV. 

— Melissa Crawley is the author of “Mr. Sorkin Goes to Washington: Shaping the President on Television’s ‘The West Wing’” and the recently released “The American Television Critic.” She has a Ph.D. in media studies and is a member of the Television Critics Association. To comment on Stay Tuned, email her at staytuned@outlook.com or follow her on Twitter at @MelissaCrawley.