Things to do in Fajardo
In-depth Fajardo guides
Longer reads for the curious. Where the activity pages tell you how to do something, these explain why Fajardo is the way it is, from the microscopic organisms that light up Laguna Grande to the lighthouse standing watch on the point.
These are the deep dives. We pull together the science and history behind the coast so a kayak trip or a stop at the reserve carries a little more meaning. Start with the two below, with more to come.
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Single-celled organisms called Pyrodinium bahamense, a type of dinoflagellate, emit a brief blue-green flash when the water around them is disturbed. Millions of them concentrate in the lagoon, so the water lights up as you paddle through it.
The glow is faint, so bright moonlight washes it out. Nights around a new moon show the strongest effect, while nights near a full moon are the weakest. Cloud cover can also help.
Despite the common name bio bay, Laguna Grande is technically a lagoon, connected to the sea by a long, narrow channel. That enclosed, calm water is part of why the organisms concentrate there.
It is a chemical reaction. A molecule called luciferin reacts with oxygen, helped by an enzyme called luciferase, and almost all the energy comes out as light rather than heat. That is why people call it cold light.
No. Laguna Grande sits in a protected reserve and swimming is not allowed. The glow is sensitive to light pollution and water quality, so the protections help keep one of Puerto Rico's few consistently bioluminescent waters healthy.
The Spanish-colonial lighthouse was completed in 1880 and first lit in 1882. It is listed on the National Register of Historic Places and stands inside the Las Cabezas de San Juan nature reserve on Fajardo's northeastern point.
Fajardo was established as a settlement in the 1700s, though sources differ on the exact year. Its historic name is Santiago de Fajardo, after its patron saint, and the town grew up around its coast and harbor.