I am a massive Andrew Mayne fan, so it wasn't even a decision to read "Sea Castle." What a thrilling, exciting and intriguing ride! Sea Castle is the fourth book in his Underwater Investigation Unit series but can be read as a standalone. Sloan McPherson of the Underwater Investigation Unit is a well-written, strong and rational character. Her interactions with hardened, reckless and impulsive Gwen Wylder create an "opposites attract" dynamic duo. Both characters are driven and passionate. The plot and the level of expertise are quite a niche, but a delightful read. The first half of the book settles the pace, establishing the premise and characters, and the second half goes all out to deliver an unexpected, thrilling and shocking ending. Having read Andrew Mayne's books earlier, I found the narrative style slightly different; however, it is refreshing.
I look forward to reading more of the UIU series. 

Thank you to NetGalley and Thomas & Mercer for giving me an ARC. This honest review is left voluntarily.