Silent as the Sea by Ava L. Mond

Grace Furst is ready to divorce her husband of five years, but there’s just one problem, he won’t sign the papers. Now, she’s stuck doing one more job with him on a cruise ship in the middle of the ocean. When Grace catches the eye of a criminal mastermind, she’ll get caught in his nefarious net over international waters. Her estranged husband, whom she’s not sure she can trust, may be her only hope.
Cameron Henderson isn’t ready to give up on his marriage and has exactly seven days to win back his wife. He’ll have to do whatever it takes and risk it all to convince her he’s the same man she married. When she winds up in the clutches of a killer, intent on taking over the ship, he’ll leap into action. Cameron must rely on his eclectic set of skills to save his wife from danger before she’s lost to him forever.