San Juan in €380s-€390s rtn from Oslo/Stockholm

Hands up, who's heard of the microscopic organism dinoflagellates?

Bear with us, we know this sounds like an odd way to start a conversation about cheap flights to Puerto Rico, but it might just be the reason you visit.

It turns out, that particular organism (found in 3 spots around the island) has a unique property when the sun goes down—it glows a bright iridescent blue!   

Sadly, it doesn't show up quite as vivid on film, so you'll just have to go see it in person. For your best chances, head to the suspiciously named Mosquito Bay in Vieques. From there, you can join a kayaking tour to really get up close and personal by gliding along the glowing waters under the moonlight.