There's definitely something fishy going on at the East London Museum. In addition to a whole section on the discovery of the coelacanth, the museum has a large display of preserved fish, including an enormous manta ray. For a different kind of fishy, check out what is claimed to be the world's only surviving dodo egg. Jurassic Park, here we come! Probably the most worthwhile exhibit, though, is the extensive beadwork collection; it's culturally interesting and just plain beautiful.
319 Oxford St., East London, 5213, South Africa