Sitting in the RA office

I am sitting in the RA office. A guy and a girl with arms around each others shoulders just came in. The girl's crotch was....wet. I only saw her from behind, and the butt part of her crotch was wet. I am assuming that the frontal/vaginal part of her crotch was also wet. I am very confused by this. I know who the guy is but I'd rather not put his name here because it would be kinda embarrassing.