Enlarge / Jack (Leonardo DiCaprio) sacrifices his spot on a makeshift raft to save Rose (Kate Winslet) in Titanic . (credit: CBS/Getty Images)

(Major spoilers for the 1997 film below. Psst: The ship sinks.)

Ever since James Cameron's blockbuster film Titanic hit movie screens in December 1997, fans have been arguing about a specific scene in which Jack (Leonardo DiCaprio) nobly gives up a spot on a makeshift raft to ensure Rose (Kate Winslet), the woman he loves, survives. Tired of constantly having to defend his artistic choice against claims that both lovers could have fit onto the raft, Cameron decided to re-create the scenario under controlled conditions in a new documentary for National Geographic: Titanic: 25 Years Later with James Cameron, marking the film's quarter-century anniversary.

For the 10 people on the planet who haven't seen the film, Jack and Rose are star-crossed lovers from different social strata who have the misfortune of consummating their love minutes before Titanic hits that infamous iceberg. (The characters are fictional, intended to humanize the tragedy by giving us someone specific to root for.) Much drama ensues, involving Rose rescuing Jack from a lower deck as the icy waters approach and engulf them and jumping off the lifeboat she briefly boarded because she can't imagine leaving Jack behind.