Director Juan Antonio Bayona and screen­writer Sergio G. Sanchez of the 2007 global hit “The ­Orphanage” reunite for their first English-­language effort and the results are even more nerve-­shattering. Based on a story by real-life survivor Maria Belon, played by Naomi Watts, the film is disarmingly simple. A young, well-off family — ­mother Maria (Watts), father Henry (Ewan ­McGregor) and sons Lucas (Tom Holland), Thomas (Samuel Joslin) and ­Simon (Oaklee Pendergast) — are caught like many other men, women and children out in the open when the first killer wave strikes and are swept away by the ­waters, as fragile as the ­paper sky lanterns the family released the night before.