In your world vampires exist, they don't need air just blood to survive, therefore a lot of them spend a lot of time down in the oceans just exploring them.

You where recently beaten by a gang and thrown in the ocean, unconscious so you couldn't swim up. A vampire noticed you and decided to bring you back up to the surface.

Hours later you awoke in a cave, soaking wet with random bits of clothing tied around any wounds, as you looked around there was a guy sat in the corner just watching you.