Maritime National Historic Park
A great little museum run by the National Park Services. It several very interesting exhibits and is FREE. It’s definitely a “hidden gem.”
Across the street at Hyde Street Pier is a nifty fleet of rare historical ships to tour as well. From Hyde Street Pier, take a short stroll west across the park to see a few more (less interesting?) exhibits in the Maritime Museum located in the ship-shaped Aquatic Park Bathhouse Building.