The Adelaide Dolphin Sanctuary spans 118 square kilometres of tidal estuary where the Port and Torrens rivers meet Gulf St Vincent, encompassing mangrove forests that stabilise 37 kilometres of shoreline. Established in 2005 under South Australia's Marine Parks Act, the sanctuary protects critical habitat for a resident population of bottlenose dolphins whose behavioural patterns — cooperative hunting in shallow water, mother-calf bonding in sheltered channels — have been documented by Flinders University researchers since the early 1990s. The protected zone extends from the Garden Island causeway north to Outer Harbor, where low-lying mudflats and seagrass meadows form a nursery for juvenile fish and a foraging ground for over 70 bird species recorded in annual wetland surveys. Port Adelaide's maritime infrastructure — wharves built for wool and wheat export in the 1880s, dredged channels that once serviced steamships bound for London — now serves a different commerce. Eco-tourism operators launch from Garden Island Road, where the sanctuary's northern boundary meets remnant saltmarsh. The mangrove belt here is Avicennia marina, grey mangrove, a species that filters tidal water through pneumatophore roots and anchors sediment deposited by winter floods. Kayakers entering these channels at dawn move through a transitional ecosystem where freshwater flow meets saline intrusion, creating brackish conditions that support estuarine species absent from open ocean. Dolphin encounters in the sanctuary are governed by strict approach protocols enforced under state wildlife interaction guidelines. Operators maintain 50-metre exclusion zones; animals that surface within paddle range do so on their own terms. Morning departures align with tidal cycles that concentrate fish schools in shallow water, increasing dolphin activity near mangrove edges. The sanctuary's ecological value extends beyond charismatic megafauna — sediment cores extracted from the Port River bed contain pollen records spanning 7,000 years, documenting post-glacial sea-level rise and the gradual formation of the estuary's current topography. Guided kayak tours operate year-round from the Garden Island staging area, where interpretive signage details the sanctuary's marine fauna and the legislative history that secured its protection. Winter months bring calmer conditions and higher dolphin visibility as reduced boat traffic limits acoustic disturbance. The sanctuary remains one of fewer than 20 urban marine protected areas globally where wild dolphins maintain year-round residence, a conservation outcome tied directly to habitat preservation and regulated human access.