His most iconic role was a swaggering, trench-coated antihero, so it makes a certain amount of sense that Judd Nelson of “The Breakfast Club” would, eventually, be cast as a pirate. In the film “Dead Water,” out Friday, the actor plays a non-campy, modern variety: “We edge toward pirate without it being swashbuckling,” Nelson, 59, tells The Post. “I do have a damaged eye in it — very close to an eye patch.” Nelson happily plays the villain in the thriller, which also features Casper Van Dien. “I think villains tend to be more realistic in the sense that they make both good and bad decisions,” he says. “A lot of heroes, all the decisions they make are good ones.” This fall he’ll also appear in the war movie “Dauntless” alongside a fellow ’80s name, C. Thomas Howell, a longtime friend. After getting his start with the so-called Brat Pack in 1985’s “St. Elmo’s Fire,” Nelson worked steadily for decades in everything from drama (“New Jack City”), to sitcom (“Suddenly Susan”), to action ...