Dead Reckoning. Sandra K. Moore

Notes from the Captain's log:My destination: An island not marked on any mapMy mission: To rescue my sister from her drug lord husband, come hell or high waterBut first, I need to figure out which of the undercover DEA agents aboard my ship–men sworn to protect Natalie and me–is a traitor.I'd been poisoned by exhaust fumes and nearly sucked into propeller blades–and these were no accidents. Unfortunately, the agent I took into my confidence–and into my bed–has been lying to me all along. Suddenly, navigating the good guys from the bad is a lot harder. But I'm one mistress and commander no one wants to cross….–Captain Christina Hampton, the Obsession