4 Best Sights in Puerto Rico

East of Esperanza, Puerto Mosquito is one of the world's best spots for a glow-in-the-dark experience with undersea dinoflagellates—microorganisms that light up when the water around them is agitated. Local operators offer kayak trips or excursions on nonpolluting boats to see the bay's light show. Look behind your boat at the twinkling wake. Even the fish that swim through and jump from the water bear an eerie glow. The high concentration of dinoflagellates sets the bay apart from other spots (including in Puerto Rico) that are home to these microorganisms. The experience is best when there's little or no moonlight; rainy nights are beautiful, too, because drops hitting the water produce ricochets that shimmer like diamonds. Note that licensed operators are prohibited from leading tours on the day before, during, and after a full moon.

The canyon may be difficult to find, but it's well worth the effort. Trails of tropical vegetation lead to a breathtaking waterfall. Tour guides can take you straight to the action while you learn about the plants and animals that inhabit this stunning region. This difficult trail is not suited for children or those with limited experience or mobility, so remember to be safe and plan accordingly.

A few miles north of Fajardo is this fishing area, where seafood is sold in open-air restaurants along the ocean. A small park in the middle of town has a lovely waterfront walk, and it's easy to find outfitters for any kind of ocean adventure, from kayak excursions to sailing trips.

Las Paylas is a series of natural rock slides and pools accessed through a path near a local's home. You can park at the home for a fee, and it's a short five-minute hike into the rainforest. People come with coolers, picnic baskets, and music to set up and relax by the water. There are bathrooms available for those who park at the home as well. If you're going to ride down the rock slides, make sure to tuck in your elbows.