Blackfish

Gabriela Cowperthwaite's 2013 investigation into the captivity of killer whales at SeaWorld devastated the company's share price, triggered congressional hearings, and ultimately led SeaWorld to end its orca breeding programme entirely. The film had a theatrical gross of just $2.1 million but its streaming impact on Netflix was seismic -- a textbook case of documentary filmmaking forcing direct corporate and legislative accountability.