Ahoy, matey! Learn about life on the high sea and find out why pirates swabbed the deck and if they actually walked the plank at Pirate Fest, offering fun for kids, live music, pirate costume contests and treasure hunt. Refreshments sold. 11am-4pm at Darnall’s Chance House Museum, Upper Marlboro. $5: 301-952-8010; www.history.pgparks.com.