Book Review: Susan Casey Takes us to the Deeps in The Underworld

The Underworld: Journeys to the Depths of the Oceans 

Doubleday: 2023, 352pp.

Susan Casey's new book is her best work: her best writing, her most fascinating topic, and the best blending of her personal adventures and the larger picture of the natural world and the people who explore it.  To be honest, I’ve also never been as envious of the adventures she undertakes or manages, by excellent networking, to get invitations to.

Casey’s Chapter 1 is a trip to Sweden to see the original Carta Marina, the famous 16^th-century illustrated map showing an incredible variety of monstrous creatures. Most, she notes, were based on fact, albeit with enormous degrees of exaggeration. This is her starting point to explore the history of deep ocean observation, the competing theories, and the slow advance of technology through the Challenger expedition. She chronicles the work of pioneering explorer William Beebe, the development of the bathyscaphe, and Trieste’s descent to the Challenger Deep (I never knew William Beebe and Theodore Roosevelt once drew submersible designs on a napkin!) 

The author threads information and stories on geology, hydrothermal vents, seaquakes, and life of every kind, from whales to bacteria, all through her narrative. She sails on the RV Atlantis with the famed ROV Jason, doing shifts as a data logger while the ROV sends back stunning images, and tours the world’s most famous submersible, Alvin. She includes many tales of disaster and near-disaster for the aquanauts. Everyone she meets reminds her that this is an environment that, while bearing life in unprecedented variety, is as hospitable to humans as deep space.

Casey introduces us to the legends of marine exploration, Don Walsh and Her Deepness, Sylvia Earle, along with a dozen or so lesser-known people who deserve to share the spotlight.  (Walsh just died at 92, literally while I was reading this book.)

The real highlight for the reader is Casey’s own experience as a submersible passenger.  I’m not sure ocean life can be described more evocatively than Casey does it on her two dives. The first is a test dive of the Neptune to a thousand meters off the Bahamas. Neptune was one of the submersibles supporting creator/funder Victor Vescovo’s Five Deeps effort (diving to the deepest point in each ocean, doing science along the way).  She is fascinated by the luminescent jellies... “a blazing purple ring with flowing white tentacles…a gold crown that throbbed like a heart...a child’s drawing of the sun.” When they turn off all lights, “It was as though we were in the center of a meteor shower, streaks and bursts and aureoles of light bejeweling the darkness to the far edges of our vision…”  For someone whose breakthrough book was about great white sharks, Casey clearly appreciates amazing life of all kinds. She even gets to drive a little. “You’re doing great,” the pilot says. “I think you’re going backwards, though.” 

Casey later gets to do a much deeper dive, to Kamaʻehuakanaloa Seamount (aka Lōʻihi) in the Hawaiian Islands on a trip with Vescovo himself to free a stuck lander. Five thousand meters down, Casey tries hard to describe the sensations of being embraced, enthralled, and awed by the scenery. “You don’t glimpse the mystery, you enter it.” Vescovo, among many other accomplishments, mentions filming a snailfish at 6,890m, then a record for finding a living fish. (The record as of this writing is a snailfish at 8,336 m.)

Casey does a great job of describing shipboard and submersible conditions and the work needed to launch, operate, and recover submersibles, ROVs, and fixed-site landers.  Much of this hardware is aimed at hydrothermal vents, whose 1977 discovery shocked everyone: It was, Casey writes, “A Star Wars bar ecosystem bar scene ecosystem that flouted all of our rules.”

She does almost as well with descriptions of the undersea environment and underlying science. If she can get a little cutesy (morphing mantle rock… “throws off heat, hydrogen, and methane in a kind of planetary hissy fit”), the complex grandeur of the topic demands the reader let her get away with it.

Casey includes detours to other fascinating topics, including more museums and the search for the world’s most valuable treasure ship, the San Jose’, finally located but “reburied” under intense legal disputes. She explores the fraught question of mining the deep sea for manganese nodules and does not have much trouble making the case that, however greenwashed such projects may be, they are a terrible idea.

For my fellow fans of unrecognized species, Casey covers William Beebe’s claims of seeing spectacular deep-sea fish that, she notes, no one has observed since.  To be charitable to Beebe, the vivid way Casey describes the self-illuminating life seen on her submersible dives, it's easy to imagine Beebe, squinting through a thick quartz window with inadequate illumination, thinking multiple animals or chained invertebrates were part of a large, illuminated fish. In interviewing Don Walsh, she does not mention his Challenger Deep sighting of a fish at almost 11 kilometers down. (Walsh had still maintained in talking to Bill Streever for his 2109 book In Oceans Deep that it may have been a fish and not a holothurian.)  Casey discusses numerous deep invertebrates discovered, many still undescribed, by ROV and submersibles.

In discussing giant squid, she includes encounters like the spectacular Pauline squid v. whale report from 1875 (which, allowing for some overestimated dimensions, could be true) and the racing trimaran Geronimo's 2003 encounter with a 10m squid that wrapped its arms around the rudder.  Casey is relatively conservative in describing the sizes of the giant and colossal squids, so it was interesting to read on page 187, “…researchers have found larger beaks from what they describe as a super-colossal colossal squid.” Her source is a 2015 article in Deep Sea News by Dr. Douglas Long, who refers to extra-large beaks found in sperm whales' stomachs. I’ll have to poke into that a bit more.  

She closes with a discussion of the future of deep-sea exploration, centered around an Explorers Club dinner that includes all the luminaries of that world. The dangers to the deep are huge: the possibilities of exploration and discovery are endless.

There are nits to pick. The USS Indianapolis was a cruiser, not a battleship. And it's odd wording when  she says, referring to underwater explorers, “I’d come to think of them as the ‘aquanauts,’" – a term in use for many decades.

There are 29 pages of page notes, four of references, and two of resources, so kudos to Casey for documentation. There’s also a very good collection of photographs, most in color, although Casey isn’t the only one to note that photography doesn’t do justice to how spectacular the depicted creatures and features look in person.

The Underworld also makes a good companion to Helen Scales' The Brilliant Abyss, with Scales providing more science and Casey conveying more the sense of wonder. Casey has turned in a five-star tour of the deep that all us landlubbers should have on our reading lists.  

 

 Matt Bille is a writer, historian, and naturalist living in Colorado Springs. He can be reached at mattsciwriter@protonmail.com. Website: www.mattbilleauthor.com.

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