Keamari is Karachi's working harbour, a gritty, salt-caked area west of the city centre where fishing boats crowd the jetties and the smell of diesel and marine life is inescapable. It lacks the polished edges of Port Grand but has considerably more genuine character: this is where the city's fishing industry actually operates, and the early morning activity — boats coming in, fish being sorted, ice being loaded — is worth seeing if you can manage the hour.
From Keamari you can hire a small boat to Manora Island, a short trip across the harbour mouth that takes you to a quiet sandy spit with a lighthouse, an old Hindu temple, and a fraction of the mainland's noise. The island is accessible and inexpensive; the boat crossing is the point as much as the destination. Manora itself is low-key and best visited for a few hours rather than a day. Back on the mainland, the streets around the jetty have basic seafood restaurants that serve the morning's catch with little ceremony and a great deal of flavour.