Andrew Mayne may have started out as a magician, but over the past 13 years he has made magic on the pages of some of the finest, most intelligent thrillers out there. DARK DIVE is his fifth Underwater Investigation Unit novel, and it may be the most intense installment yet.

Mayne writes what he knows, and this series, which stars professional diver Sloan McPherson and her Underwater Investigation Unit team, plays directly into one of his soft spots. A few years ago, Mayne hosted a show during the now-infamous Shark Week where he dove with great white sharks in Australia and invented a suit that would make him appear invisible. It was brilliant stuff, and all of that love for diving is given to this first-class series.

"The action and underwater landscape in DARK DIVE is non-stop, and Andrew Mayne makes it so easy to visualize this brave new world found beneath the depths of some notorious Florida sinkholes."

The Prologue finds us in Central Florida in the year 11,867 BCE. We witness a young woman named Niqua being chased by something evil that had killed most of her tribe and was now forcing her into the Darkland. This same area plays a big role in DARK DIVE in the form of some dives made at various sinkholes that might be the gateway to another era.

Sloan and her partner, Scott Hughes, accompany their boss, George Solar, to a Florida lake with an interesting problem. It appears that a van carrying a bunch of cadavers crashed into the lake and sank. The driver barely got out, and his body was covered in alligator bites. It is now the next mission of the UIU not only to put a hook on the vehicle so it can be dragged out, but to avoid being eaten in the water. This is a lot to ask as a van full of literal human chum has just been dumped into a lake filled with some enormous gators.

Sloan has a close call on this dive and has to be rescued by Scott. Either way, it’s great for them to be back on the job after their unit had been briefly defunded in the previous novel, SEA CASTLE, before the powers that be saw the value in them. Sloan does not have much time to enjoy herself when she receives word that a legendary Florida diver and longtime family friend, Fred Stafford, has disappeared. She takes it upon herself to look into this disturbing development, and eventually it becomes a case for the entire team to handle.

Sloan begins with Fred’s girlfriend, who has not seen him for a week and is very concerned. Because of Fred’s skills, he is often asked to assist with diving missions around the globe, though he is typically never out of touch for this long. One lead that could be valuable is the Dive Rats, a trio of divers with whom Fred formed a dive club. They might know what he was up to or if any of their recent dives had been dangerous and caused him to go back on his own.

The primary Dive Rats are Liza Yurinov; her husband, Pete Langshire; and a wealthy young man named Ed Buelman. They all seem legit and don’t appear to be hiding anything, but they are unable to offer any information that could help locate Fred. They invite Sloan and Scott to come to their next dive into some dangerous Central Florida sinkholes, known as the Devil’s Cauldron, that boast a complex underwater cave system.

Sloan and Scott investigate various sinkhole dive spots in the area and end up finding Fred’s abandoned truck by one of them, but nothing else worthwhile and no body. Further checks into Fred’s background show that he might not have been the person Sloan always thought he was. He had a bad gambling habit and a secret past that I will not reveal here.

The action and underwater landscape in DARK DIVE is non-stop, and Andrew Mayne makes it so easy to visualize this brave new world found beneath the depths of some notorious Florida sinkholes. At one point, there’s a crossover with another series of his when Sloan reaches out to Dr. Theo Cray. I enjoy tips of the hat and fictional worldbuilding like that! This very personal case for Sloan becomes a true missing person/murder mystery. Hold your nose and dive in, because Mayne has some nice surprises for you under the surface of this novel.