Too bad “Washington, D.C.’s only maritime music festival” isn’t thus because its organizers set up a naval blockade at the southern point of East Potomac Park. (“Try to muscle in on our salty sea shanties, eat a cannonball.”) But the Capital Maritime Music Festival is family-friendly, with concerts and workshops celebrating the maritime culture of the Potomac River, Chesapeake Bay, and C&O Canal. Veteran folk artist Bob Zentz, cosplayers The Washington Revels, and “Songs of the War of 1812” with the Ship’s Company Chanteymen are just a few of the 11-hour event’s water-worthy attractions.