Picked by Underwater Investigation Unit fans

Here are 9 books that Underwater Investigation Unit fans have personally recommended once you finish the Underwater Investigation Unit series. Shepherd is a community of authors and super-readers sharing their favorite books with the world.

Book cover of Into the Planet: My Life as a Cave Diver

Nicholas Harvey Author Of Twelve Mile Bank

From my list on female scuba diving thrillers and mysteries.

Why am I passionate about this?

My wife suggested we try scuba diving while on holiday in Grand Cayman. We were already falling in love with the island, and the incredible experience underwater opened a whole new world to us. From that moment on, our yearly travels changed completely. Our destination choices were now based upon diving opportunities. That was twenty years ago. Today, I’m a certified divemaster with dives all over the US (including Hawaii), the Caribbean (including Cuba), Australia, and even Iceland. Throw in my sense of adventure as a former race car driver, motorcycle rider, and outdoor adventurer, and I had plenty of personal experiences to create the AJ Bailey series.

Nicholas' book list on female scuba diving thrillers and mysteries

Nicholas Harvey Why Nicholas loves this book

Jill isn’t only the world’s top female cave diver, she’s one of the best, period. What’s amazing about this book is how it reads like a hair-raising fantastical adventure tale, yet it’s all true.

I’ve dabbled in cave diving in the cenotes of Mexico, and it is certainly addictive stuff, but I can’t imagine going to the places Jill has risked her life to discover.

This could easily have been a choice in my females who kick-ass list as well!

By Jill Heinerth ,

Why should I read it?

1 author picked Into the Planet as one of their favorite books, and they share why you should read it.

What is this book about?

From one of the world’s most renowned cave divers, a firsthand account of exploring the earth’s final frontier: the hidden depths of our oceans and the sunken caves inside our planet

More people have died exploring underwater caves than climbing Mount Everest, and we know more about deep space than we do about the depths of our oceans. From one of the top cave divers working today—and one of the very few women in her field—Into the Planet blends science, adventure, and memoir to bring readers face-to-face with the terror and beauty of earth’s remaining unknowns and the extremes of…


Book cover of Swimming with the Dead: An Underwater Investigation

Nicholas Harvey Author Of Twelve Mile Bank

From my list on female scuba diving thrillers and mysteries.

Why am I passionate about this?

My wife suggested we try scuba diving while on holiday in Grand Cayman. We were already falling in love with the island, and the incredible experience underwater opened a whole new world to us. From that moment on, our yearly travels changed completely. Our destination choices were now based upon diving opportunities. That was twenty years ago. Today, I’m a certified divemaster with dives all over the US (including Hawaii), the Caribbean (including Cuba), Australia, and even Iceland. Throw in my sense of adventure as a former race car driver, motorcycle rider, and outdoor adventurer, and I had plenty of personal experiences to create the AJ Bailey series.

Nicholas' book list on female scuba diving thrillers and mysteries

Nicholas Harvey Why Nicholas loves this book

Kathy’s series – which I wish she’d continue one day – inspired me to include my passion for scuba diving in my novels. Her main character, Hannah Sampson, is a member of the Denver Underwater CSI team, who’s asked to help the police in the British Virgin Islands investigate a case. Needless to say, she stays on the island for the following books and becomes embroiled in hair-raising cases that challenge her above and below the water.

Kathy published her series at a time when very few novels centered around diving, and certainly didn’t include a female protagonist. I found her work transported me to the islands, and enthused me to create AJ Bailey and subsequently, Nora Sommer.

By Kathy Brandt ,

Why should I read it?

1 author picked Swimming with the Dead as one of their favorite books, and they share why you should read it.

What is this book about?

Murder runs deep in a thrilling new series.
An Underwater Investigation featuring C.S.I. diver Hannah Sampson.

Summoned to the sun-drenched beaches of the British Virgin Islands, Hannah Sampson is fully prepared to face unknowable dangers beneath the crystal-clear waters of an idyllic paradise. But the possibility of murder runs deeper and darker than the sea itself. Her police commissioner's son-an expert diver and researcher-was found dead, pinned under the submerged wreckage of a cargo ship. Whatever the victim was looking for, he found.

Whatever he found was the death of him. Now Hannah must discover for herself what lies beneath-a…


Book cover of Deep Shadow

Sharon Ward Author Of In Deep

From my list on mysteries set on a tropical island.

Why am I passionate about this?

Even as a kid, I was intrigued by the underwater world, so as an adult, I learned to scuba dive. I took to it like a fish to water, and my husband and I spent the next several years traveling to tropical islands to experience the local dive conditions whenever possible. I loved learning how every island had a different culture and a different undersea environment. Since I love tropical islands, scuba diving, mysteries, and adventure stories, these books really hit my sweet spot.

Sharon's book list on mysteries set on a tropical island

Sharon Ward Why Sharon loves this book

As a long-time diver, I was enthralled by the details of the undersea world. Set on the tropical island of Bonaire, a scuba diver’s paradise, this book introduces the reader to two great characters, divemasters Boone Fischer and Emily Durand. 

The author interweaves Boone and Emily’s budding romance with compelling descriptions of the diving and the sea life they encounter. The way the two divemasters get involved in the search for the drug submarine at the heart of the mystery is plausible. Twists and turns on every page keep the reader guessing about the fate of the sub, its crew, the cruise ship, and most critically, the two highly appealing divemasters who use every skill they have to avert disaster. I was instantly hooked on the series.

By Nick Sullivan ,

Why should I read it?

2 authors picked Deep Shadow as one of their favorite books, and they share why you should read it.

What is this book about?

In the turquoise waters of the Caribbean, something lethal is on the move.

Scuba divers travel from all over the world to visit the little island of Bonaire, with its crystal-clear waters and a host of beautiful marine life. After three years in the “Diver's Paradise”, divemaster Boone Fischer thought he’d seen it all; but on a routine afternoon dive, he spots something that will turn his tranquil life upside down.

From the arid shores of the ABC Islands to the tropical jungles of Venezuela—from the ocean depths of the Southern Caribbean, to the lush islands of the Northern Leewards,…


Book cover of Deep: Freediving, Renegade Science, and What the Ocean Tells Us about Ourselves

Nicholas Harvey Author Of Twelve Mile Bank

From my list on female scuba diving thrillers and mysteries.

Why am I passionate about this?

My wife suggested we try scuba diving while on holiday in Grand Cayman. We were already falling in love with the island, and the incredible experience underwater opened a whole new world to us. From that moment on, our yearly travels changed completely. Our destination choices were now based upon diving opportunities. That was twenty years ago. Today, I’m a certified divemaster with dives all over the US (including Hawaii), the Caribbean (including Cuba), Australia, and even Iceland. Throw in my sense of adventure as a former race car driver, motorcycle rider, and outdoor adventurer, and I had plenty of personal experiences to create the AJ Bailey series.

Nicholas' book list on female scuba diving thrillers and mysteries

Nicholas Harvey Why Nicholas loves this book

Okay, so Deep isn’t specifically about women, or scuba diving – it tackles freediving – but includes females and anyone who loves diving in any form should read this book. The meticulous research into the physiology and psychology of human beings underwater is simply fascinating. Nestor ventures off into all kinds of territory, from octopus intelligence; to whales conversing; to humans holding a single breath for an inhuman amount of time.

Freediving is the common theme in the book, but it is far more than that. This is an in-depth study of life beneath the waves from an intriguing perspective.

By James Nestor ,

Why should I read it?

1 author picked Deep as one of their favorite books, and they share why you should read it.

What is this book about?

From the author of the international Bestseller Breath

Covering a diving championship in Greece on a hot and sticky assignment for Outside magazine, James Nestor discovered free diving. He had stumbled on one of the most extreme sports in existence: a quest to extend the frontiers of human experience, in which divers descend without breathing equipment, for hundreds of feet below the water, for minutes after they should have died from lack of oxygen. Sometimes they emerge unconscious, or bleeding from the nose and ears, and sometimes they don't come up at all.

The free divers were Nestor's way into…


Book cover of Angel Killer

Gigi Pandian Author Of Under Lock & Skeleton Key: A Secret Staircase Mystery

From my list on mysteries with solutions you’ll never see coming.

Why am I passionate about this?

I’ve always been drawn to locked-room mysteries, the baffling mysteries where the crime looks truly impossible. The mystery becomes not only who did it, but also how. It’s the ultimate puzzle. The best locked-room mysteries include gothic elements that make you wonder if something supernatural is responsible, but then are resolved with a satisfying rational explanation—like Scooby-Doo for adults. I’ve written more than a dozen mystery novels, but until now, I’ve only focused on locked-room mysteries in my short fiction. In my new Secret Staircase mystery series, I’m focusing on these puzzles in my novels. Here, I’m sharing some of my favorite locked-room mysteries that feature truly ingenious puzzles. 

Gigi's book list on mysteries with solutions you’ll never see coming

Gigi Pandian Why Gigi loves this book

Multiple ingenious impossible crimes feature into the first Jessica Blackwood thriller by magician Andrew Mayne. A killer calling himself the Warlock claims to be using supernatural powers to perform deadly miracles, and only former stage magician Jessica Blackwood, now an FBI agent, can see through his tricks. Because magicians create misdirection for a living, they’re perfect characters to unravel seemingly impossible crimes. As a bonus, Jessica Blackwood is a terrific character you’ll root for. 

By Andrew Mayne ,

Why should I read it?

1 author picked Angel Killer as one of their favorite books, and they share why you should read it.

What is this book about?

Meet Jessica Blackwood, FBI Agent and ex-illusionist.

Called in because of her past to offer expertise on the mysterious 'Warlock' case, Jessica must put all her unique knowledge to the test as the FBI try to catch a ruthless killer.

Needing to solve the unsolvable, and with the clock ticking, they're banking on her being the only one able to see beyond the Warlock's illusions.

The first in a brilliant new series, Angel Killer will have you feverishly turning the pages, and in Jessica Blackwood, Mayne has created a complex, sassy and unforgettable new heroine.

'Professional illusionist Mayne introduces a…


Book cover of Hag's Nook

Gigi Pandian Author Of Under Lock & Skeleton Key: A Secret Staircase Mystery

From my list on mysteries with solutions you’ll never see coming.

Why am I passionate about this?

I’ve always been drawn to locked-room mysteries, the baffling mysteries where the crime looks truly impossible. The mystery becomes not only who did it, but also how. It’s the ultimate puzzle. The best locked-room mysteries include gothic elements that make you wonder if something supernatural is responsible, but then are resolved with a satisfying rational explanation—like Scooby-Doo for adults. I’ve written more than a dozen mystery novels, but until now, I’ve only focused on locked-room mysteries in my short fiction. In my new Secret Staircase mystery series, I’m focusing on these puzzles in my novels. Here, I’m sharing some of my favorite locked-room mysteries that feature truly ingenious puzzles. 

Gigi's book list on mysteries with solutions you’ll never see coming

Gigi Pandian Why Gigi loves this book

No author is more famous for writing locked-room mysteries than John Dickson Carr. Hag’s Nook is the first of Carr’s novels featuring Dr. Gideon Fell, who went on to become Carr’s most well-known detective. It features a family curse and an isolated English countryside home with a view of prison ruins on “Hag’s Nook,” a site where witches were once hung—and where the family curse is about to play out once more when the eldest son is required to spend an hour inside the prison to inherit the family fortune. Spooky and brilliant, this is a great introduction to Carr. I hope you’ll fall in love with it and go on to read many more of his books.

By John Dickson Carr ,

Why should I read it?

1 author picked Hag's Nook as one of their favorite books, and they share why you should read it.

What is this book about?

'The Starberths die of broken necks' goes the legend in the village of Chatterham . . .

The Starberth family governed the now-abandoned Chatterham prison for many years, and each male heir must spend the night of his twenty-fifth birthday there, alone, overlooking the hanging site of Hag's Nook.

Meanwhile, after a chance encounter on a railway platform, Dorothy Starberth and young American graduate Tad Rampole fall in love. Rampole is here in rural Lincolnshire to see Gideon Fell. The following day, Dorothy's brother is found dead of a broken neck, just as his father and grandfather before him.

Ingeniously…


Book cover of Hercule Poirot's Christmas

Trevor D'Silva Author Of A Bloody Hot Summer

From my list on Agatha Christie and Sir Arthur Conan Doyle.

Why am I passionate about this?

Even though I’m an engineer and accountant by education, I love to write and growing up, I read many historical fiction and murder mysteries. History spanning from the Victorian Era until the mid-twentieth century has always fascinated me, and I’ve studied various events from that period. Therefore, I wrote A Bloody Hot Summer, a crime novel using some historical events as a background. The interwar years were the heyday of crime fiction, and that is why I set my novel during that period. While researching, I get to expand my knowledge regarding history, culture, art, language, and values of those times, which I add to the novel.

Trevor's book list on Agatha Christie and Sir Arthur Conan Doyle

Trevor D'Silva Why Trevor loves this book

In this book, a murder takes place in a manor house just like in my novel, but during Christmas time. There is a connection to a diamond mine in South Africa, and how that played a part in the murder of the patriarch of the family. Detective Hercule Poirot has to delve into the family’s past to connect the dots and determine the motive and the identity of the killer. For those who like murders set during Christmas time, this is a novel for you.

By Agatha Christie ,

Why should I read it?

3 authors picked Hercule Poirot's Christmas as one of their favorite books, and they share why you should read it.

What is this book about?

It is Christmas Eve. The Lee family reunion is shattered by a deafening crash of furniture, followed by a high-pitched wailing scream. Upstairs, the tyrannical Simeon Lee lies dead in a pool of blood, his throat slashed.

But when Hercule Poirot, who is staying in the village with a friend for Christmas, offers to assist, he finds an atmosphere not of mourning but of mutual suspicion. It seems everyone had their own reason to hate the old man...


Book cover of The Tokyo Zodiac Murders

Queenie Chan Author Of The Dreaming Volume 1

From my list on Manga & novels that are mysteries from Japan.

Why am I passionate about this?

I’ve always been a fan of dark stories and unsolved mysteries. As I grew older, this led me to read true crime, historical mysteries, horror stories, and mystery detective fiction. I also have a preference for classic stories from decades gone by, as I have a strong interest in how genre-defining stories that appear at a certain time can have great influence over a generation of writers. So, it’s fitting to say that all my recommendations tend to be great stories from long ago. Much like the Sherlock Holmes stories by Arthur Conan Doyle, people still read these stories today and probably will in the future since great stories are timeless.

Queenie's book list on Manga & novels that are mysteries from Japan

Queenie Chan Why Queenie loves this book

I like macabre mysteries with compelling hooks and clever resolutions that blow my mind, and this book does exactly that. Japan has a long tradition of writing “fair play” mysteries, which they call honkaku novels. These borrow from the Golden Age of Detective Fiction in the vein of Agatha Christie but certainly are their own category. 

These novels are like puzzles, focusing on the rules of fair play by giving readers all they need to figure out the mystery. This story was my first honkaku story and is only the length of a novella (like many honkaku novels), and it’s also rather dark, which I enjoy since I like horror as much as mystery.

By Soji Shimada , Ross Mackenzie (translator) , Shika Mackenzie (translator)

Why should I read it?

2 authors picked The Tokyo Zodiac Murders as one of their favorite books, and they share why you should read it.

What is this book about?

'If you like your crime stories to be bloody and bizarre, then this one may be for you. The winner of several major awards... the solution is one of the most original that I've ever read' Anthony Horowitz

A bestselling and internationally-acclaimed masterpiece of the locked-room mystery genre

Japan, 1936. An old eccentric artist living with seven women has been found dead - in a room locked from the inside. His diaries reveal alchemy, astrology and a complicated plan to kill all seven women. Shortly afterwards, the plan is carried out: the women are found dismembered and buried across rural…


Book cover of The Devil and the Dark Water

Gigi Pandian Author Of Under Lock & Skeleton Key: A Secret Staircase Mystery

From my list on mysteries with solutions you’ll never see coming.

Why am I passionate about this?

I’ve always been drawn to locked-room mysteries, the baffling mysteries where the crime looks truly impossible. The mystery becomes not only who did it, but also how. It’s the ultimate puzzle. The best locked-room mysteries include gothic elements that make you wonder if something supernatural is responsible, but then are resolved with a satisfying rational explanation—like Scooby-Doo for adults. I’ve written more than a dozen mystery novels, but until now, I’ve only focused on locked-room mysteries in my short fiction. In my new Secret Staircase mystery series, I’m focusing on these puzzles in my novels. Here, I’m sharing some of my favorite locked-room mysteries that feature truly ingenious puzzles. 

Gigi's book list on mysteries with solutions you’ll never see coming

Gigi Pandian Why Gigi loves this book

Set on a treacherous sea voyage in 1634, this impossible crime is cloaked by an atmospheric setting. Is a demon hiding on the ship—or is there a very real killer stalking victims in the claustrophobic setting? This was unlike any locked-room mystery I’d ever read, and it was impossible not to get swept up in the adventure on the high seas. With detective Samuel Pipps accused of a crime and imprisoned in cramped quarters on the ship, it’s up to his bodyguard to act on his behalf and prove a human hand—not a demon—is responsible for the murder and mayhem aboard.

By Stuart Turton ,

Why should I read it?

2 authors picked The Devil and the Dark Water as one of their favorite books, and they share why you should read it.

What is this book about?

'If you read one book this year, make sure it's this one' Daily Mail CHOSEN AS A BOOK OF THE YEAR BY THE GUARDIAN, SUNDAY TIMES, DAILY MAIL, FINANCIAL TIMES, DAILY EXPRESS AND i PAPER WINNER OF THE BOOKS ARE MY BAG READERS AWARD FOR FICTION SELECTED FOR THE BBC TWO BOOK CLUB BETWEEN THE COVERS AND THE RADIO 2 JO WHILEY BOOK CLUB An impossible murder A remarkable detective duo A demon who may or may not exist It's 1634 and Samuel Pipps, the world's greatest detective, is being transported from the Dutch East Indies to Amsterdam, where he…