It’s a sunny autumn afternoon in Brisbane, Queensland, in the north of Australia. The weather never gets too cold up here; overcoats are rarely worn. The prosperous, up-and-coming city is served by ferries that ply the Brisbane River, which in the steamy summer months can resemble the muddy, slow-flowing Mississippi.

On May 9, between 10:00 am and 4:00 pm, the ferries running to the University of Queensland deviated from their path and paused for a moment, facing the opposite bank, where they were greeted by a small group of Aborigines. The action was unannounced and almost indiscernible; for