Victor Harbor's maritime economy shifted from whaling station to wildlife sanctuary in less than a century. Encounter Bay earned its name in 1802 when Matthew Flinders met Nicolas Baudin here during competing surveys of the Australian coast; by the 1840s the harbor served as South Australia's first deep-water port, and by the 1870s local whalers processed southern right whales within sight of Granite Island. The last whale was taken in 1872. Today the same waters host a resident population of approximately 150 bottlenose dolphins, their presence documented year-round by marine biologists from Flinders University who track pod movements between the Bluff and Wright Island. The granite outcrop connected to the mainland by a 630-metre causeway is home to a breeding colony of long-nosed fur seals, established in the early 1990s after the species' near-extinction during the colonial sealing era. Victor Harbor dolphin cruise operators depart from the causeway's western jetty, navigating the shallow channels where dolphins hunt garfish and Australian salmon. Tours typically circle Granite Island's southern cliffs before entering deeper water off Rosetta Head, where pelagic birds—shy albatross, Cape Barren geese, and occasionally migratory short-tailed shearwaters—follow fishing activity. The Big Duck, a purpose-built 12-metre vessel with underwater viewing ports, began operations in 2018 and now runs four daily departures during peak season, with hydrophone equipment allowing passengers to hear dolphin echolocation clicks in real time. The Fleurieu Peninsula's coastal shelf drops to 40 metres within two kilometres of shore, creating nutrient upwellings that sustain dense schools of pilchards and southern calamari. This bathymetry explains why Victor Harbor dolphin cruise tours encounter marine life consistently across seasons—winter brings juvenile southern right whales on their northward migration, while summer months see increased surface activity as dolphins herd baitfish into the shallows. The South Australian government designated Encounter Marine Park in 2012, imposing speed limits and no-take zones that have measurably increased both fish stocks and dolphin pod sizes. Local operators follow a voluntary code requiring 100-metre separation from cetaceans and prohibiting swimmer interactions, standards enforced by the state's Marine Parks division. Morning departures between 9:00 and 11:00 typically offer the calmest conditions and highest dolphin activity, as pods move inshore to feed during the tidal change.