Night Swim features a shocking death scene that is never explained by the movie, even in the ending. Night Swim follows the Waller story of the family, a set of unfortunate suburbanites who purchase a new home only to discover their pool is haunted. This might sound like the setup for a silly supernatural spoof, but no one is left laughing by Night Swim’s grim ending. The Blumhouse horror movie takes its zany premise surprisingly seriously, which didn’t help the mixed reviews received by the PG-13 effort upon its January release.
https://screenrant.com/night-swim-pool-spirit-rules-cat-death-not-explained/