Romance\Mystery Story Tips?

Teen girl is on vacation with her family. (Camping? At a resort? In a big city hotel? On a cruise ship? You decide.) She meets a boy and they go off to find a private place to talk and hang out, and they witness a man doing something odd (digging something up and rushing off with it? leaving someone else's room with a bag of something? running away from a dead body?) Or they just find a body or maybe hear that things are being stolen, and they want to investigate.