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Puerto Rico is tropical, mostly warm and mostly wet.

But the southwest corner is a little drier and more desert-like than the rest.

Cacti and other succulents grow on the sandy dunes leading down to the crystalline sea.

Many of the visitors who come here arrive in town by car.

They explore the waterfront and its plaza and take in its bustling restaurants,

loud noises and bright lights. But you've come here for a different reason.

You're here to experience the natural wonder of this place.

It's bioluminescent bay.

Bioluminescence is when a living organism produces light.

Here on the coast of Puerto Rico is one of the world's best examples of this phenomenon.

And that is what you've come to see.

On a typical day, tour boats depart the busy docks every evening, taking people to see the bay.

If you'd come here any other day, that's how you might have visited it too.

But tonight is special.

There are no boats leaving as the sun begins to set.

Their engines are quiet. And the docks creak softly as the boats bob up and down beside them.

Instead, we will drive down to the coast a little, walk to the beach and swim our way out into the bay.

...