Most people don't know they know a sea chantey, but they do — whether it's "What Do You Do with a Drunken Sailor?," "Good Night Ladies," and "Michael, Row the Boat Ashore," or something incredibly obscene that after 150 years of social progress still isn't fit for polite company. That's because sea chanties are sailor songs, and people out at sea for months at a time tend to lose touch with niceties like manners. Since the Bay Area is the epicenter of America's folk music scene, you can bet that the monthly Sea Chantey Sing on the Hyde Street Pier is recognized from coast to coast as a place where the masters of the music come to lead the crowd. It's held from 8 p.m. to midnight on the first Saturday of every month; after 11 p.m., even the filthy songs are fair game. If that isn't enough to get you to go, it's held on board the historic tall ship Balclutha; hot chocolate, coffee, and cider are served; and it's all free.