Port Lincoln is a working seafood town on Boston Bay, near the southern tip of the Eyre Peninsula. It has grain silos, fishing boats, tuna money, and a marina full of serious charter vessels, but the reason travellers make the long haul from Adelaide is the coast around it.
The headline experience is shark cage diving at the Neptune Islands, one of the few places in the world where visitors can reliably get in the water with great white sharks. Less theatrical but often just as memorable are the sea-lion swims, oyster trips, and tuna stories that come with a town built around the Southern Ocean.
On land, Lincoln National Park starts just south of town, with granite headlands, sheltered bays, emus, kangaroos, and views over one of Australia's great natural harbours. Whalers Way is rougher and more dramatic: cliffs, blowholes, islands, and Southern Ocean weather.
Port Lincoln is not a quick side trip. The drive from Adelaide is long, though flights make it easy enough for a short break. If you are already exploring the Eyre Peninsula, it is one of the places where the region's scale, seafood, wildlife, and exposed coast come together.