You know you’d have accepted the bet too. Admit it.
The title doesn't do this fic any favours. This one has more plot than porn, with a PG-13 rating for the first part which only makes it to an R in the second story. But I think it's an interesting and vaguely plausible scenario they put themselves into, and the thought of sex up against a palm tree on the beach is one I'm happy to entertain.