"Submarine. Lots of soldiers and Ice Warriors." That's how "Doctor Who" star Jenna-Louise Coleman summed up "Cold War" episode.

In the episode debuting at 7 p.m. CT April 13 on BBC America, the Doctor (Matt Smith) and Clara (Coleman) land the TARDIS in 1983 and inside a Russian nuclear submarine whose captain (played by "Games of Thrones" actor Liam Cunningham) is already dealing with another surprise guest--an Ice Warrior.

Fans haven't seen the classic "Doctor Who" foes that first appeard in 1967 to fight Patrick Troughton's Second Doctor since the 1970s. In the 2009 special "The Waters of Mars," the Tenth Doctor (David Tennant) gave them a shout out, calling them "a fine and noble race who built an empire out of snow."

Current showrunner Steven Moffat didn't plan on bringing them back. He said during a recent conference call with reporters that he wasn't a fan, but the episode's writer, Mark Gatiss, "kept nagging me about bringing them back and then he came up with an idea, which ... really made them come to life for me."

"So at that point I really got into it," he said, "but that was Mark's creativity rather than mine."

Because the Ice Warriors aren't as familiar to modern audiences--and like many classic "Who" foes they seemed a little cheesy--the show's designers had to improve on the design for today's high-def TVs. The result is realistic and scary.

The designers also earned Moffat's praise for the realistic look of the submarine.

"I think they did a stunning job on that. It's just really, really convincing you that you're on board a sub. At every level I just thought that was a bit of a design triumph," he said.

"It's one of those things that you always wonder: Will it just look like some corridors? But no, the art department really sold that. Michael Pickwood had a field day with that and it was brilliant."

The submarine looks realistic, but the water used to douse it and the actors was the real thing, Coleman joked in a separate interview.

"It was very wet!" she told me. "We actually did the whole thing proper, so instead of going into makeup, we were made down by being soaked. They had buckets of water and all sorts of things every day. We were kind of up to our ankles [in water] from flooding the sets, and they used underwater cameras.

"But it's a great episode."

Watch the teaser for the Douglas Mackinnon-directed "Cold War" below.


Want more? Discuss this article and others on Show Patrol's Facebook page