Half the population of the planet has been wiped out by an apocalyptic virus on "The Last Ship," and even though a cure has been found, it still isn't smooth sailing for the USS Nathan James in Season 2. There are two groups of people who want to prevent CDR Tom Chandler (Eric Dane) and Dr. Rachel Scott (Rhona Mitra) from distributing the newly discovered vaccine for free -- and they aren't shy in their attempts to try to gain control.

The first group is the greedy, who want to make money off of the world's misery. The second group is those who think they are the chosen because they are naturally immune, so they want to run the world.

"They won't be special anymore if the cure gets out there and makes everyone just like them," executive producer Hank Steinberg told FOX411 at Comic-Con. "They're led by a really great new character, Sean Ramsey [Brían F. O'Byrne], who's like a cult leader.  He also happens to have control of a submarine. So the enemies are going to be extremely formidable, and it's going to be really fun to watch that play out over the course of the whole season."

In addition to Sean and his faction of Immunes, including his brother Ned [Nick Court], Season 2 has seen the addition of  two new crew members aboard the Nathan James -- joining from Israel is Lt. Ravit Bivas (Inbar Lavi) and from Australia is SCPO Wolf Taylor -- both of who know their way around hand-to-hand combat and weapons.

"New characters spice things up and it's also natural to the storytelling, because they're going to need people that have skill sets that can help them," Steinberg says.

Not to mention that Bivas and Taylor are hot, so there is definite interest in them romantically from fellow crew members.

"It's really a fun balance to play when you have these small character moments, where people are able to let their guard down and be vulnerable. They have real meaning and impact, so unlike on a soap opera where everyone is walking in every 5 seconds and talking about their feelings. These are very selfless people, selfless heroes. They have wants and desires and needs, but they're trying to sublimate those to the higher calling. I think that tension makes it interesting."

What's been incredible for "The Last Ship" is the cooperation they have received from the U.S. Navy, which has allowed them to film onboard actual ships, and even provided them access to the hospital ship that was used as the USNS Solace in the July 5th episode.

"The Navy has been incredibly supportive and excited," Steinberg says. "We had a big premiere in Washington, D.C., where thousands of military people showed up. The Secretary of the Navy [Ray Mabus] himself has been to our set and actually recorded a cameo. It's the episode where they find the message that was buried in the files of the White House. The guy who's playing the Secretary of the Navy, is the real Secretary of the Navy."

The inspiration for "The Last Ship" was the thought of what might happen if global warming were to melt the polar caps and release an ancient microbe from melted permafrost in the Arctic. If it had been buried long enough ago, the majority of the population of the planet wouldn't have built up any kind of immunity to it, so its release would be devastating.

"I'm deeply concerned about global warming," Steinberg says. "I mean, it's 110 degrees right now in Rome. It's 90-plus in Portland, which never gets weather like that. We haven't dealt with it that much on the show in terms of verbalizing it, but this is a global-warming catastrophe show. As to people not really talking about it on the show, they've got bigger fish to fry. They've got to deal with the problem in front of them and try to solve it."

"The Last Ship" airs Sunday nights on TNT.