Keeper of the lost cities and Harry Potter crossover

Who are these people!

Hermione's POV

We were walking around the school grounds when all of a sudden these people come out of nowhere and almost run into us. I shrieked and      almost dropped my books. Then I saw that they were in bathing suits. "OMG is she ok?!?" I asked. I saw a teenage girl passed out in a boys arms. Then a face I had not seen for a while stepped out from behind a boy with teal eyes and brown hair. "Hey guys!" Sophie said. I didn't say anything but I ran over and hugged her. Ron and Harry ran over and we had a group hug. The boy with brown hair asked something but he said it in a different language and I didn't understand. Sophie answered back and she was blushing. "Sophie who are these people?" The brown haired guys asked. "Fitz these are my friends from when I went on a school trip. And no I'm not dating one of the guys. Hermione is dating Draco, Ron is dating Lavender, and Harry is dating Ginny." She introduced us all and then all of a sudden there was a flash of light and Sophie snapped her fingers and they were all dressed in fighting suits. Then Voldemort appeared with people behind him.