When the words “true story” appear twice in a film’s opening disclaimer, it’s a guarantee that what follows will include at least one questionable fiction. The Impossible is inspired by the Alvarez Belons, a Spanish family of five who survived the 2004 Indian Ocean tsunami that claimed almost 300,000 lives; in the film, the Iberian quintet has been remade into a more “relatable” British clan headed by Ewan McGregor (as businessman Henry) and Naomi Watts (as Maria, a physician who left her practice to be a full-time mom). Currently stationed in Japan, Henry, Maria, and their three boys, ranging in age from about 12 to 5, have arrived in Khao Lak, Thailand, for the Christmas holiday. The enormous waves that battered that country (and many others) on December 26 are staggeringly staged by director J.A. Bayona (2007’s The Orphanage)—a feat of dubious distinction. (Does verisimilitude to actual disaster serve any purpose besides, as Susan Sontag wrote, allowing “one [to] participate in the fantasy of living through one’s own death”?) Separated from Henry and the two younger children, Maria— trailing pools of blood from a muscle-deep gash as she deliriously trudges through brackish water—and the oldest son, Lucas (Tom Holland), eventually make it to a chaotic hospital. These horrors, and the absorbing performances of Watts and McGregor, will soon be undermined by a surfeit of sentiment.