Deep Waters (The Security Specialists, 1)

DUTY TO PROTECT Thirty feet underwater when her oxygen tank fails, Caley Flynn fears it's been sabotaged—and she'll be the next to die. Her intern's already dead, her home breached and something's amiss at her Florida marine-life rescue center...but no one believes she's in danger. Except Shepherd Lightman. When Caley's brother asked him to check on her, the marine turned security specialist hoped it would be a case of calming down a nervous veterinarian. But the threats are all too real. Rescuing Caley and remaining alive isn't easy, but resisting his boss's sister is where the real danger lies. Because with his heart in the balance, he'll do whatever it takes to stop a killer who's desperate to keep a secret hidden.