Killer Mermaid (2014)

Kelly and Lucy go on vacation to the Mediterranean to visit their friend Alex, who used to date Lucy back in college. Lucy, who wants to rekindle things with Alex, is surprised to discover he's engaged. Awkward, especially since everyone will be staying at Alex's home.   The good news is they've got plenty of dance music and alcohol. So everyone gets trashed and dances. Meanwhile a young couple is killed near the water by a man with a fishing implement of death.

The next day while having a drink at a local cafe, they run into Bob, an old friend of Yasmin. He says they should go explore the abandoned prison on a nearby island.  An old  salty sea dog at a nearby table issues a wordy warning to stay away from the prison.  But since he's creepy and old, they ignore his words.

They head out to the island and roam through the old buildings. But soon they discover they are not alone.  There is a man on the island doing something sketchy. This alerts our intrepid explorers that they should get the hell out of there.

Unfortunately they aren't the brightest people and betray their presence. Their deflated boat hinders their escape. So they hide while they figure out how they're going to get off the island.  This leads to the familiar cliche where people split up and then won't consider leaving without the others.

For a movie called Killer Mermaid, there's not a heck of a lot of mermaid in it.  She shows up about half way into the film.  Even then, they think she's a girl being held captive because they can only see her face.  She sings her siren song and bewitches the men. Although apparently it isn't all that bewitching because all it takes to break her spell is a solid slap to the face.

And if you think it takes a long time to get her involved in the story, it takes even longer for her to start killing.  It's too bad because it would have been much better if she kept picking people off throughout the movie, until the end she flops onto the pavement and isn't very threatening at all.