South Australia set aside an entire dolphin sanctuary by act of parliament in 2005 — roughly 118 square kilometres of mangrove, tidal creek and open water north of the city — for animals no one can compel to appear. Adelaide 4 Hour Swimming With Dolphins Experience Tours leave from the other end of that same coastline, at Marina Pier in Glenelg, into the sheltered water of Gulf St Vincent. The dolphins here are Indo-Pacific bottlenose, Tursiops aduncus, a smaller and more coastal animal than the offshore bottlenose familiar from documentaries. Glenelg is the oldest European settlement on the South Australian mainland. Colonel William Light's survey party came ashore at Holdfast Bay in 1836, and the colony was proclaimed beneath a gum tree that still stands a short walk inland. The suburb that grew around it became Adelaide's seaside room: a tram line laid down to the sand, a jetty rebuilt after a century of storms, and much later the Holdfast Shores marina cut in behind a breakwater. Marina Pier sits inside that harbour, on Holdfast Promenade. The tram from the city runs twelve kilometres to Moseley Square, and the boats leave on a bearing that has not shifted much in a hundred years. What has shifted is the relationship. The gulf's seagrass meadows — Posidonia and Amphibolis — anchor a food web of garfish, squid and mullet, and the resident pods follow it season by season. Individual animals are catalogued by the nicks and scars along their dorsal fins, and some have been logged in the same few kilometres of water for more than twenty years. Under national marine mammal guidelines, swimmers hold a line trailed behind the vessel: the dolphins are neither fed nor touched, and they leave when they decide to. Nothing about the encounter is choreographed. Sightings are likely rather than promised, which is the honest arrangement every Glenelg wild dolphin swim cruise makes with its passengers before the engine starts. The sanctuary proper is a different proposition again, and a different hull. Kayaks thread the mangrove channels of the Port River, where calves are raised in water shallow enough to stand in. Cruises pass the Ships Graveyard off Garden Island, where the ribs of scuttled coastal traders rust in the shallows, colonised now by cormorants. Between those two coastlines sits the full spread of Adelaide dolphin tours — catamaran watching trips, eco kayaking, sanctuary cruises, and the long ferry crossings that run south toward Kangaroo Island. Among them, the Adelaide 4 Hour Swimming With Dolphins Experience Tour remains the only one that asks a visitor to get in the water and wait.