Here’s all that I can recall;

-A school teacher is dating unbeknownst to her a killer
-He shows her a picture of a girl and claims it’s his daughter, but is actually just a picture he ripped from a magazine
– He lures a girl ( from her class i believe) with a puppy, kills the puppy, and eventually the girl
– In the end he recovers the dead body of the girl from the water and walks out of the water with the dead girl, with the school teacher watching on the beach