On holiday or not, you're not the type to hook up with the first guy in shorts who walks past. You need time to get involved with someone and you like to really get to know them. He'll need to have plenty of interests that match your own.
Who? A friend of the family, a student who's come to revise at his grandmother's, a divorced family man…
Plus points: Your common interests bring you together and you can spend hours on end talking. You're never short of ideas for somewhere to go or something to do.
Downsides: By playing the romantic card, you risk losing time and transforming him into a friend instead of a lover.
Chances of it lasting: It's highly likely that this sweet story will survive across the seasons and miles. There's no reason that your relationship, built up over time, will disappear once summer is gone.