South African Naval Museum
By far the best of the town's various museums, this rather detailed space is filled with model ships, antique navigational equipment, old South African Navy divers' equipment, a few actual life-size boats, and, oddly enough, a helicopter. Interesting, too, are the murals in the old naval church, and some of the stories of rescue missions and naval heroes over the years. The newer "Transformation" section includes a display about the SS Mendi and information about how the navy has changed in democratic South Africa. It's staffed by passionate naval personnel, so you can come armed with intricate questions.
