Question: is 47 meters below based on a true story

Answer: No, 47 Meters Down is a British-American 2017 survival horror film directed by Johannes Roberts, written by Roberts and Ernest Riera, and starring Claire Holt and Mandy Moore. The plot follows two sisters who go on holiday in Mexico, and are invited to cage dive and see sharks up close. When the cable holding the cage breaks and it plummets to the ocean floor with the two girls trapped inside, they must find a way to escape, with their air supplies running low and great white sharks stalking nearby.