In Too Deep by Catherine Mann

Love at first sight in a tropical paradise isn’t all it seems. Not when he’s undercover.

C-17 copilot Darcy Renshaw wants a piece of the war-zone action like the rest of her Air Force family. Instead she’s stuck on a peace-time mission hauling a brooding marine biologist and his dolphins to Guam, thanks to her over-protective 5-star father. Or so she thinks…
CIA Agent Max Keegan needs a low profile, military airlift to a South Pacific island. He doesn’t need First Lieutenant Darcy Renshaw busting his cover and bringing chaos into his top secret Naval Marine Program investigating underwater wire taps. All the same, he can’t suppress the urge to protect one reckless – enticing – lady pilot.
Soon, Darcy finds more turmoil than she bargained for in Max’s arms … and at the hands of an assassin who won’t rest until Max loses everything.