Stuck... With them?!?! (One Direction Fanfiction)

'The last thing I remember? Being at a boat party for my older cousin's 21st. Where am I now? On some island. Am I alone? I don't know... and it scares me.'

Meet Lizbeth; 18, short, medium build, blonde hair with natural red and brown high and low lights, blue/grey eyes, lived on a farm till her mother divorced her father and moved to the 'big city' with her new boyfriend when she was 10. She doesn't have many friends and is an only child. The only thing/person she confides in is a beaten old journal she has had for most of her life.

Lizbeth was sitting by a railing at the back of the boat, writing in her journal. She had been trying to get away from the loud music... some band had been playing when she escaped to her hiding space. The boat took a sharp turn and Lizbeth fell into the ocean below and passed out.

Now she's stuck on an island, in the middle of nowhere and as far as she can tell, with no one else.

As the boat turned sharply another person fell over board, Zayn Malik. Now, seeing as the boys don't think things through, they all jumped in after him to help. As they're helping keep him afloat Niall notices another shape in the water close to them...

Who or what is it?