Daring Her Seal by Anne Marsh

Devil–may–care Navy SEAL Levi Brandon faces a terrifying task: telling Ashley Dixon that their faux wedding during their last mission together was actually real. It's bad enough that she completely loathes him, but she's DEA. Levi will be lucky to get away with his life… 

Now Ashley and Levi have returned to Fantasy Island to sort things out…and are tempted to play a dangerous game of lust and restraint. A game of dares. All Levi has to do is keep himself from having sex with the hottie DEA agent. But Ashley's playing to win–and darers always go first.