Vieques Island, Puerto Rico

Just after 5 p.m. we got into our room in Esperanza on Vieques, an island of the eastern coast of Puerto Rico that until 2003 had been occupied by the U.S. Navy so it’s relatively undeveloped. That evening we maneuvered kayaks into Mosquito Bay for a bioluminescent tour.

Bioluminescence is the phenomenon that makes fireflies glow. In the bay the bioluminescence is produduced by organisms called dinoflagellates. Any time they are disturbed, they light up.

We paddled out about a quarter mile in the bay in darkness broken only by the faint light of the moon, secured our boats to the guide’s and jumped out to swim. Well, Mark didn’t. He doesn’t swim. He was pretty scared for his first kayak paddle despite the fact that the water was only about 5 feet deep and if he stood flat-footed on the ocean floor, the moonlight would have glanced off his shoulders.

Streaks of light slid down my arms and fingers as I kept them moving in the water. The bioluminescence is obvious but the organisms producing the light are invisible. Like the lightning bug’s light, the dinoflagellite’s glow extinguishes in two or three seconds.

Mark, with a view from above in his kayak, said it seemed I had a neon green aura when I kicked my legs wide as I swam. He said I look like a ghost. According to NationalGeographic.com, each gallon of water in Mosquito Bay holds about 750,000 dinoflagellates. So when I swam, Mark was seeing millions and millions of dinoflagellates lighting my way.

Dinoflagellates even lit up in the water in Mark’s kayak, he said.

After a surreal half an hour, we rowed in, each paddle stroke illuminated. Fish zipped along near the surface, leaving a neon green jet stream.

The tour operator told us that the dinoflagellates use bioluminescence as a defense mechanism: They light up fish that are looking to dine on them so that predators of these fish can see them to eat before the dinoflagellates themselves are eaten. It sounds reasonable, but research returned nothing to back up this claim.

I don’t care why they do it, I’m just glad we had a chance to see a bioluminescent colony before the dinoflagellates go extinct.

There are two dinoflagellate colonies accessible from Puerto Rico. The best, most populated is the one we visited because no motorized boats tour the bay. Tour companies offer glass-bottom boat rides to a colony off the southwest coast of the main island, but pollution from boat motors is destroying the dinoflagellates; the tour companies are putting themselves out of business.

Swimming with dinoflagellates, even seeing them in the bottom of your kayak as Mark did, makes for a more memorable, first-hand—and fingers and legs— experience, I think. And no guilt.

If you go, go natural.