The Barker Inlet estuary holds one of the world's few urban dolphin populations — roughly 30 Indo-Pacific bottlenose dolphins that have claimed the mangrove-lined shallows between Garden Island and the Port River as permanent feeding grounds. The Adelaide Dolphin Sanctuary, gazetted in 2005 across 118 square kilometres of tidal flats and samphire beds, protects these resident pods while allowing kayakers to trace the same muddy channels the dolphins patrol for mullet and garfish. The sanctuary's most surreal landmark lies half-submerged in the northern shallows: a cluster of decommissioned iron barges, ferries, and coastal steamers left to rust in place since the 1950s, their hulls breached by decades of salt corrosion and tidal surge. The ships graveyard exists because Port Adelaide, once South Australia's busiest maritime gateway, had no formal shipbreaking industry. Obsolete vessels were simply moored in shallow water near Garden Island and abandoned, their timber stripped for salvage while iron skeletons remained. Today the rusting hulls serve as artificial reefs, their interiors colonised by barnacles, algae, and juvenile fish that attract the dolphins. A Port Adelaide dolphin sanctuary kayak tour typically launches from the Garden Island boat ramp at high tide, when water depth allows paddlers to navigate close to the wrecks without grounding. The mangrove forests lining the estuary are grey mangroves, Avicennia marina, adapted to hypersaline soils and visible at low tide by their dense thickets of pneumatophores — vertical breathing roots that puncture the mud like stubble. Dolphin sightings occur year-round, though the pod's ranging behaviour shifts with the seasons. Winter months see dolphins concentrate near the Port River mouth, where schools of Australian salmon migrate. Summer disperses the pod across the sanctuary's northern reaches, including the mangrove channels and the wreck zone. The sanctuary's free-entry status and proximity to Adelaide's northern suburbs make it South Australia's most accessible marine wildlife encounter. Kayakers share the water with recreational anglers, kite surfers, and occasional pelicans that roost on the corroded masts of the sunken ships. The estuary's muddy opacity means dolphins often surface within arm's reach before paddlers register their presence — a dorsal fin cutting the surface, then gone.