The beach fishing is second to none: a fishing rod will soon have a couple of good sized flathead in the bag. Squid can be caught from the end of the jetty at night, under the light. Huge Oysters and mussels can be collected off the rocks past the boat ramp at low tide.
Interesting places to visit around Southport and far south Tasmania: Hastings Caves; Ida Bay Railway; Tahune Airwalk; Dover Musuem & Gallery and Ida Bay Railway Lines. Take a picnic lunch and drive 30 minutes to Cockle Creek to see the whale sculpture and THE very end of the road in Far South Tasmania.
As far as activities are concerned, as Southport is a coastal town, think about fun on the water!