This 4th installment in the series is entertaining and thrilling.

The UIU is on hiatus due to some political and jurisdictional problems, so Sloan McPherson is currently working for the Florida Department of Law Enforcement until all those issues are sorted. When she's called to the scene on a Fort Lauderdale beach, she becomes involved in what may be a serial killer case. She's paired with Gwen Wylder, an unpopular homicide detective from Miami, and they investigate various cold cases involving missing women and murder.

This was very good and I really enjoy the character of Sloan McPherson. I like this author's writing style and the complicated and interesting plots. This was quite different to the previous books in the series, and that made it even better to show more dimensions of the main character. The narrative takes some unexpected turns and the conclusion was quite surprising. I definitely recommend this series and suggest it be read in order.

Thank you to NetGalley and Thomas & Mercer for this e-book ARC to read and review. I look forward to the next book when the Underwater Investigation Unit might be back in action.

<i>ARC provided by NetGalley for an Honest Review</i>
Sea Castle was another action packed sea-venture in the series. From start to finish the book was interesting and engaging. I was immediately sucked back into this world even though it’s been awhile since I’ve read the last one. While the book could be read as a standalone it’s highly recommended you read the series in order for both continuity and an understanding of the heroines history & background. By the end this was a pretty insane read once the twisted killer was revealed. So scary that someone so evil could be able to manipulate technology like an expert level hacker. While I was mildly shocked about the villain this book read more like Criminal Minds episode towards the end than the CSI Miami vibes I’ve gotten in previous books. I’m a fan of both so zero complaints from me as I kinda liked the more psychological aspect of this book. A killer that preys on vulnerable women like a twisted cultist is honestly terrifying to me. The way people such as sociopaths are able to manipulate and control other human beings, heck their very lives, is something most of us could never grasp. And now with technology it’s even easier for people to connect and even spy or stalk victims if your skilled enough. Sloan seemed even more badass in this book and as always I truly love her backbone. Also seems she’s finally gaining the reputation she deserves among her peers. I mean she’s a badass cop and something fierce/fearless in water. She’s the total package for law enforcement in the Miami are 😛 I listened to the audio of this book and have nothing bad to say. The narrator definitely helped build up the tense moments and made for a wonderful and intense read!

Thank you to Netgalley and the publishers for this ARC copy. I give this honest review voluntarily.
This is another installment of the Sloan McPherson saga that is as engaging as the last one. I have read Sea Storm and do own the first two books, The Girl Beneath the Sea and Black Coral, but I haven't yet read the first two-- they are on my reading list but the list is very long. In this go around Sloan McPherson is not a police diver because the Underwater Investigation Unit is under review as to whether or not it will continue. Sloan's regular partner, Scott Hughes decided to take further training as opposed to working like Sloan for the Florida Department of Law Enforcement as a seat filler. She eventually gets teamed up with an old dog detective Gwen Wylder who many think is crazy. She has a short fuse temper and is difficult to work with but I still find myself liking this character and she keeps Sloan very busy on multiple cases. Sloan and Gwen circle back to the case that began the book--- a woman found dead in the ocean. They discover that this is not a single person death but a number of women killed by a serial killer. I won't say anymore to spoil it for anyone reading this review who hasn't read the book yet but needless to say it is a great read and I highly recommend it. I'm hoping Mr. Mayne continues with this series because I just love this smart, strong, and interesting female lead character. I give this novel 4 ¾ stars.

I loved this addition to the Under Water investigation unit. I will say though that there was a pretty big lack of under water investigating in this book. However, this book took an entirely different direction than the first three books but it made for a really great read. This one was fast paced, intense, smart and kept me guessing. I love the main character and the new characters in this one were intriguing and had quite a bit of depth. The main mystery was very well done, I had no clue what was going on until the very end. I also loved the little side mysteries in the book and the ways that they were solved. Loved it and am already eagerly awaiting the next book!

Sea Castle is the fourth installment of the Underwater Investigation Unit and is such a great continuation of the series. I want to be Sloan McPherson when I grow up. While there are far less underwater / ocean themed scenes in this read, I still found it absolutely compelling and could not wait to see where the investigation was going. And the way it ends with a sort of cliffhanger has me in such anticipation of the fifth book. This is a well written mystery and I definitely did not see where the case was going and found myself flipping back to see how Sloan and her new temporary partner Gwen came up with their rapid fire thought processes. The tension level and twists in this one kept me reading far past my bedtime.
Thank you to Netgalley and Thomas & Mercer for the opportunity to read this in exchange for my honest opinion.

The fourth book in Underwater Investigation Unit series is another great read. Sloan is an interesting character to follow as she solves crime as a forensic diver. There was less ocean/underwater time this book, but still overall an intriguing mystery.

While this story took place more on land than in the sea it was still very engaging and entertaining. Sloan was a bit easier to handle in this book.

This is the 4th installment in Andrew Mayne's series, Underwater Investigation Unit. I have now read all 4 of them and I am really enjoying the series. It is about a detective unit that does deep diving investigations of murders along the Florida coast. Love the settings, Love the storylines, Love the characters. The characters are well-developed - you feel like you know them and you can easily get invested in their lives. The investigations are, for the most part, realistic with twists and turns that keep you guessing. And each novel introduces you to a different beautiful Florida coastline setting. Can't wait for the next one! Fun and entertaining read!

I had never read any books in this series but I'm wasting no time playing catchup. Set in Florida, Sloan works in the Underwater investigations unit which is experiencing a suspension of duty due to politics. When a young woman is found dead on a local beach she is called out to take a look at the scene. I knew I was going to be reading past my bedtime from the first chapter. The plot is twisty, the characters are well developed and the dialog moves at a smooth pace with just enough humor. When I was only half way through it I had given it a spot on my TBR shelf. It's that good.
My thanks to the publisher Thomas & Mercer and to NetGalley for giving me an advance copy in exchange for my honest review.

Sloan McPherson has been a controversial and effective character since her introduction, but in Sea Castle she is dealt one of the most difficult hands ever. The Underwater Investigative Unit (UIU) is part of the Florida Department of Law Enforcement, but being as divisive as they are puts them on the edge of extinction.

McPherson is a dedicated public servant who is light years ahead of everyone else in her field, but that doesn’t keep her from answering light night calls when a body is involved. Sloan responds to a mysterious death on a beach locally that has law enforcement scrambling for answers. Because of McPhersons brashness and sometimes unorthodox techniques, no one wants her UIU team working under their banner. This leads to Sloan teaming up with a unique and serious Miami Detective by the name of Gwen Wylder.

As the team of Wylder and McPherson are on the hunt for clues, another young woman goes missing in North Carolina. The mysterious surroundings of Carla Burgh’s disappearance and magical reappearance lead Sloan and Gwen on a road trip that changes the entire outlook of the story. Pulling all the stops out, Gwen and Sloan track down another woman who was mentally ‘kidnapped’ only to have their case stalled and misdirected many different ways. McPherson must weather the storm and team up with one of the most dynamic personalities on the force to bring those responsible for the murder of another young woman.

Sloan McPherson is tenacious and unwavering, leaving worry behind to find justice in Sea Castle. Andrew Mayne keeps you glued to the pages with lives at risk and psychopaths on the loose. The buildup to the final run is very tame and tempered while the answers to your questions are seemingly in front of you the whole time. Mayne also shows the selflessness and unwavering dedication that local law enforcement emulates day after day in our respective communities. Bleeding fierceness and truth, Mayne has another great book on his hands

Andrew Mayne is an underrated thriller writer, but his books about police diver and detective Sloan McPherson are always a good read, especially if you are holidaying near the coast.

Sea Castle is his latest book about Sloan and the Florida Underwater Investigation Unit, and opens in typically evocative manner with Sloan recovering water-logged evidence at night from the murder scene of a young woman on a Fort Lauderdale beach. From there it powers off in unexpected directions as Sloan becomes caught up in the search for a possible serial killer.

Sea Castle sees Sloan reluctantly teamed up with Gwen Wylder, a Miami homicide detective notorious for being manipulative, reclusive, rude and terribly smart. Gwen agrees to help Sloan with her investigation into the girl discovered on the beach, but in return she wants Sloan’s fresh insight into seemingly unrelated cold-case murders and disappearances. As the loose ends of the old files begin to come together another woman disappears, and Sloan and Gwen find themselves in a race against time.

This is a fast paced and unpretentious crime thriller that smoothly winds it way through a good twisty plot that is full of incidents and action. Sloan is an engaging character, with an interesting backstory and nicely cynical view of police work, and she always makes for an enjoyable guide through the backwaters and gritty corners of Florida. The other characters are also well sketched and credible, and the introduction of Gwen Wylder adds a interesting new dimension to the series.

There is less of the water based action that has been a compelling feature of previous books, but Sea Castle is still a brisk and entertaining read that will easily satisfy fans of fast paced police novels

This book has great writing with an exciting ending. I liked the pairing of Gwen and Sloan because they balanced each other out and worked well as a team.

Thank you to NetGalley and Thomas & Mercer for the ARC in exchange for my honest review!

Andrew Mayne brings action, suspense, and mystery to Sea Castle, the fourth novel in the Underwater Investigation Unit series. Sloan McPherson, temporarily reassigned to the Florida Department of Law Enforcement from the Underwater Investigation Unit (UIU), is called in to consult when a young woman washes ashore on a Fort Lauderdale, Florida beach. Sloan believes the woman has been murdered, but others aren’t so sure.

For answers, Sloan reaches out to Miami homicide detective Gwen Wylder. Gwen demands fresh insight into some cold-case murders and disappearances in exchange for her help. As the old cases are worked, another woman disappears. Sloan and Gwen are sure she’s the latest in a deadly chain. However, this case isn’t straightforward.

This novel is very different from previous novels in the series with Sloan and her old partner Scott Hughes from the UIU being reassigned. Sloan takes center stage in this one with cameo appearances by Scott Hughes and their previous boss, George Solar. However, it still has amazing characterization and a solid mystery to solve.
Sloan has good reflexes and amazing instincts. She also has a discerning sense of justice and determination that makes it easy for readers to get behind. However, she takes risks and has trouble with people who ignore clues and go for the quick resolution. Gwen is manipulative, argumentative, abrasive, and rude. She’s also extremely smart, a great detective, and she’s always the victim’s ally.

The plot is complex and has twists and turns to keep a reader guessing. It easily transports readers into the terrifying world of the victims and the investigators. The high stakes kept me engaged throughout the story. The well-written story and the incredible characters combine with action and multiple mysteries to culminate in an amazing conclusion. Mayne is an exceptional storyteller who provides readers with gripping scenes that move at a blistering pace. The final chapter provides the thread for the next book in the series. My main quibble with this book was I missed the diving and underwater aspects that have made this series unique among law enforcement and police procedurals. Themes include deaths, disappearances, political pressure, family, friendship, and much more.

Overall, this was an intense story with complex characters that kept me turning the pages. I was surprised several times by events. This kept the tension level high throughout the book. There was enough background in the novel that it worked well as a standalone, but I am looking forward to reading the first two books as I wait on the next one in the series. Those who enjoy crime thrillers, mysteries, and police procedurals may want to check out this novel.

Thomas & Mercer and Andrew Mayne provided a digital ARC of this novel via NetGalley. This is my honest review. All thoughts and opinions expressed in this review are my own. Publication date is currently expected to be February 21, 2023. This review was originally posted at Mystery and Suspense Magazine.

Sloan McPherson is called to the scene of a woman that has been washed ashore. Very quickly she realizes that local police is pushing for it to be suicide or an accident, by her gut tells her murder. An under the breath comment leads her to team up with Gwen Wylder who has quite the reputation. Gwen finds a missing person and is convinced that they have only 5 more days to find her alive.
So many twists and turns, and ending is so not expected. Excellent read! And the teaser at the end just makes you count the days until the next book.

Has Sloan McPherson Become An Adult?

McPherson is called down to a crime scene on the beach. A woman was discovered with only a rope around her neck that leads out into the water. When the rope was pulled in, it was cleanly cut with no frayed end. A detective spots something floating in the water. McPherson swims out and retrieves the object. It is a plastic bag. The forensic technician opens it and discovers that it contains only clothes, probably those of the dead woman. The Underwater Investigative Unit currently in bureaucratic limbo, and her current boss in the Florida Department of Law Enforcement (FDLE) does not want any involvement in this case. McPherson has a different opinion. From this conflict, a gripping main storyline proceeds.

This novel’s main storyline is different than those in the previous novels in this series. The Underwater Investigation Unit is currently in bureaucratic limbo. The team was split and reassigned to different positions with in the FDLE. The other members start with only cameo appearances, but their roles become more substantial as the novel proceeds. The main storyline is one investigation that expands and some interesting side investigations. McPherson is partnered with a particularly abrasive detective. There are the usual twists and turns, and one tsunami that changed my entire understanding of was happening. Tension is maintained as previous murders appear to be tied with this murder, and current kidnapping that meets the murder’s modus operandi that turns very personal. The flow of the novel is rapid like the previous novel. I found the change of characters quite intriguing, especially the abrasive detective. These enhanced my reading enjoyment, and my attention was quickly captured and maintained.

The B-storyline for McPherson is very different here. The reader sees how McPherson adapts to the abrasive detective with whom she must cooperate and seems to be a match for her. This is a side that I had not seen with McPherson before. Another interesting change in this novel is McPherson’s change of attitude to impulsive actions. Looking over all the novels in this series, this change can be seen as C-storyline over the series as a whole. The abusive detective is a significant character in this novel. Much background on her is provided and the interaction between her and McPherson also enhanced my reading enjoyment.

As for the aspects of a novel that spoil the reading for some readers, there are not any intimate scenes. The level of vulgar and rude language is a noticeable but does not rise to a significant level that could be objectionable to most readers. Most of the violence is described after the fact or by inference. There are references to the events in previous novel in this series, but adequate background to understand they were her previous over-the-top behavior. If you have read the previous novels, a smile probably will come to your face as it did mine.
Even though McPherson no longer is reckless but still a hard charger, I could not find anything that I disliked about this novel In fact, this is exactly of this change of being a strong adventure without the more over the top action that resulted in my thoroughly enjoying reading this novel. I do recommend reading this novel. The author again demonstrated to me that he is one of my Must-Read authors. I rate this novel with five stars.

I received a free prepublication e-book version of this novel through NetGalley from Thomas & Mercer. My review is based only on my own reading experience of this book. I wish to thank Thomas & Mercer for the opportunity to read and review this novel early.

I've been enjoying Andrew Mayne's Underwater Investigation Unit series immensely, and Sea Castle is the best one yet. Through police diver Sloan McPherson, Mayne has been instrumental in changing my rather antiquated view of mothers in dangerous professions, and once the scales were removed from my eyes, my enjoyment of these compelling stories grew-- especially when Sloan began tempering her tendency to leap into danger without thinking with some good, old-fashioned common sense. It's been a pleasure to watch Sloan grow as she gains experience. She's truly gifted in searching for clues and putting them together, and if you're in a life-or-death situation, she's the type of person you want on your side.

With the Underwater Investigation Unit disbanded and its members working in other divisions, Sloan finds herself working for a boss who hates her. When she doesn't agree with everyone else that the young woman found on the beach died accidentally, her search for help leads her to one of the more interesting characters I've read in quite some time. Gwen Wylder is a gifted homicide detective whose talent and unstoppable determination have made her a pariah. No one wants to work with her, and spreading rumors about her level of sanity and her work ethic seems to be a favorite pastime of her fellow officers. After years of working in this toxic environment, it's no wonder that Gwen is extremely paranoid, bitter, and manipulative. Sloan herself has raised more than a few eyebrows (and doubts) in her short career, and she's used to being considered the crazy one. Pairing her with Gwen Wylder on the hunt for a serial killer really tests how much she's matured in her job.

When someone says, "A lot of this is Gwentuition and Sloanology," I had to laugh. These two have their own ways of doing things, and it was a delight watching them learn to work together-- Sloan especially since, for the first time, she's the one reining in someone else instead of someone doing that to her.

This fast-paced story kept me guessing, and the identity of the serial killer really surprised me-- something that doesn't happen very often. Although everything is tied up by book's end, it does end on a cliffhanger that makes me wish that the next book in this series were available now. Bring it on!

Sea Castle, Underwater Investigation Unit #4, is a fast paced mystery. Andrew Mayne changes things a bit in this installment. Sloan McPherson, our main character, is working with Gwen Wylder, a veteran police detective, biding her time until retirement, to solve the crime(s). We are told that Sloan's partner, Scott, is on a training exercise.

The naked body of a woman is found floating, She is identified as Nicole Donnelly from Atlanta. There is a rope tied around her neck, strangled, yes, but not by the rope, so begins Sloan's investigation. She enlists the help of Detective Wylder who agrees with the caveat that Sloan look into an unrelated cold case for her. Clues lead to a conclusion that Donnelly's death is one in a series.

I was disappointed in this installment with how little underwater action there was and the limited appearances of characters from the previous books, Sloan's father, her daughter, significant other.

This is a well written police procedural. The author throws in some twists and turns. I felt the ending was abrupt. Although this is a part of a series, it can be read as a standalone. I would recommend reading the previous books, they are well written and provide the backstory to the Underwater Unit and Sloan.

Thank you to NetGalley for an ARC. The review is my own.

I read the previous three books in Andrew Mayne's UIU series and I can safely say Sea Castle is my favorite! It's packed with humour (as usual), thrilling and emotional details, the plot is much more unpredictable than it was in the previous three, you will enjoy plot twists and red herrings too, I'd say it's more of a psychological thriller (and this is good for me). I also love how the author succeded in further developing the protagonist, Sloan, in each book of the series, there's something that changes in her as time passes by and she experiences new challenges.

Wow. This book, Sea Castle by Andrew Mayne, its twists, turns, and complete 360°s kept me on my toes.

Sloan McPherson, now assigned to the FDLE (FL Dept of Law Enforcement) after the small unit of the Underwater Investigation Unit is disbanded and she is "assigned" to a supervisor who doesn't quite know how to handle her while her former partner Scott Hughes is off training and George Solar is off being George Solar.
When a body washes up on a beach and things start to not make sense, questions lead her to the doorstep of infamous detective Gwen Wylder (interesting last name).

This is Book 4 of 4 of the Underwater Investigation Unit. There is something that makes it so difficult for me to read the last book in a series. I never want to say goodbye to characters. You don't particularly fall in love with these characters but you feel a vested interest in Sloan. I'm vested in her well being and the well being of her family (um, Run, work on that marriage thing. I know she says she doesn't want it but do it anyway.). This case or series of cases really took on some serious head and heart strings. The dangers of the Internet, lost kids, and who the predator ends up being. There were several times in this book when I physically felt like I had been punched in the gut.

Sloan, in the end, used some real smooth skills. Something she probably would later credit back to Solar. And Gwen. Well, I'm not spoiling it for you.

A must read for fans of the UIU. Well done, Andrew Mayne!

One really needs to read the preceding books in the series or else you flounder with the characters.
I wasn’t sure was Sloane was assigned to do except close cold cases?
I personally liked crusty Griff Gwen because her approach was nonsensical and direct. I bought she and Sloan made a good team.
The plot was unusual and unique which made for good reading.