The National Maritime Museum in housed in a historic Dutch warehouse within the Galle Fort. It offers an interesting glimpse into Sri Lanka's maritime history. Despite being hit hard by the 2004 tsunami, the museum has been rebuilt and now showcases a range of artifacts, including ancient shipwreck finds and exhibits on local fishing communities.

I personally found this museum to be skippable but if you have extra time and want to fill your day this is a nice option.