Based on the 1980 movie "The Blue Lagoon".
The ability of any two people to fall in love when there is no one else available.
Also the ability of the only person in a group of a certain gender to become the object of desire for the rest.
See also: proximity infatuation
A: "So how did you two get married?"
B: "Completely Blue Lagoon Syndrome. We were stranded in an elevator together over Christmas Break, so it was inevitable."
A: "I don't get it, everybody at work thinks Suzi is such a babe!"
B: "Dude, Suzi is the *only* female in your office, of course they think she's hot, it's Blue Lagoon Syndrome!"