Out of Her Depth by Brenda Hiatt

No fear was her new motto. But she never expected to be targeted for murder.
Indiana housewife Wynne Seally is determined to put her life back together after her husband leaves her for a younger woman. Traveling alone to Aruba and learning to scuba dive seem like big steps in that direction.
However, Wynne plunges in over her head when an underwater discovery turns out to be a clue in a high-profile murder case. With the help of handsome insurance investigator Ronan Gale, she soon finds herself embroiled in unraveling clues that could set an accused man free . . . or get her killed.