Finally, a mile into this late-night adventure, the canal opens onto a wide, glassy-topped bay. Sweating, panting, with blisters forming on our palms, we've arrived at the still waters of Fajardo, about an hour east of San Juan.
Laguna Grande is home to hundreds of thousands of single-celled bioluminescent dinoflagellates - tiny plantlike organisms that glow neon-blue when disturbed. On moonless nights like this, the tiny organisms provide the only source of light in the bay. We sluice our hands through the water. It sparkles, shimmers and glitters.
We quickly lash the seven kayaks together and jump into the water, letting the phosphorescent microorganisms light up our bodies and transforming this clutch of adults into a gaggle of giggling big kids.
Finding adventure in Puerto Rico is as easy as finding a rum drink in Old San Juan.
The compact island makes it easy to do three very different activities in as many days: Hike through a rain forest, snorkel off an island and frolic in the darkness in a bioluminescent bay.
And you'll still find time to sip that rum punch in Old San Juan or tour the Bacardi Rum headquarters.
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Laguna Grande, part of the larger Mosquito Bay, is one of the best places in the world to swim with the stars. The stars, of course, being the aforementioned dinoflagellates.
The paddling through the canal is rigorous, and children afraid of the dark might be scared out of their wits. But it's worth the trip.
We lie on our backs in the bathtub-warm water and wave our arms and legs up and down, back and forth, creating images of sparkly angels as the glow surrounds us. I bicycle-paddle furiously, churning the water beneath me into a foamy, shiny froth.
Thirty minutes later we reluctantly clamber back into our kayaks, calmer, fatigued and still completely in awe of this wonder of nature.
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El Yunque Rain Forest is the only tropical rain forest in the U.S. National Forest System. More than 100 billion gallons of rain fall each year on the 28,000 acres of El Yunque, and some of that precipitation is falling on this day, in stops and starts. By now the creeks are engorged.
Our small group of about 10 climbs slippery stone steps leading to La Coca Falls, a setting reminiscent of "Survivor" or "Gilligan's Island."
Everything seems bigger, wetter, louder and more pungent in the rain forest, from the iguana we spy lounging atop his favorite preening place to the quarter-sized snails inching along the foliage.
Thirteen hiking trails crisscross the terrain, which is home to more than 240 kinds of trees, as well as orchids, the tiny coqui (tree frog) and the cotorra, the endangered green parrot of Puerto Rico.
Despite our guide's best efforts on the two-hour walk, we scatter shotgun style from the falls to the gift shop before climbing over the guard rail to take a peek at Iggy the iguana, one of El Yunque's mascots. Tiny lizards careen across the tangle of tropical flowers, the color of Kansas prairie sunsets.
From the top of the 1,575-foot Yokahu Tower, we have a 360- degree view of this section of the forest. When the sun breaks through the rain clouds, we see the ocean breaking and the spires and cathedrals of Old San Juan.
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Three of us catch the 90-minute ferry ride one morning from Fajardo to Dewey, the only town on one of Puerto Rico's most popular snorkeling sites, Culebra island.
At Culebra Divers, we rent our gear ($12.50), and a small bus takes us, for another $2, to Playa Flamenco, a few miles away on a blacktop road
It's early, but the sand already scorches our bare feet. We slip and slide up over the berm and scramble to find a shady space to stash our gear.
The wide, white-sand beach curves from rocky point to mountain slope. A nesting area for sea turtles is taped off on one end; the rusting hulk of an American tank sits at the surf's edge on the other end, an angry reminder of the days when Culebra was used by the U.S. Navy.
We scatter toward reefs. The waves are easy to power through, and the snorkeling is easy too, even for the first-timer among us.
The hours pass quickly as we explore several sites. We snorkel near the tank but back away when the surf shoves us toward ugly jags of rusting metal. We gingerly crawl over and around oversized volcanic boulders, taking care to not slice our bare feet on the jagged edges.
After returning our gear, we step into the tiny bar next door. We've just enough time to order a potent rum and Coke for the ferry ride back to Fajardo.
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If you go
Getting there: All major airlines travel to San Juan. Because Puerto Rico is a U.S. territory, American citizens do not need a passport or a visa.
Lodging: Hotels in San Juan range from the exclusive Ritz- Carlton San Juan Hotel, Spa and Casino to the family-friendly Courtyard by Marriott San Juan Isle Verde to privately owned places like the Hotel Miramar.
High season runs from mid-December through mid-April.
Dining: On the short list:
The Parrot Club, 363 Calle Fortaleza, Old San Juan. (787) 725- 7370. Nuevo Latino cuisine.
La Bombonera, 259 Calle San Francisco, Old San Juan. (787) 722- 0658. Known for its strong coffee, pastries.
Ajili Mojili: 1502 Avenue Ashford in the upscale Condado neighborhood. (787) 725-9195. Traditional Puerto Rican fare.
