In the tropics, going to a place called 'Mosquito Bay' just after sunset would seem like a silly thing to do. But on Vieques, a satellite island of Puerto Rico, it's foolish not to. Also known as Bio Bay, this secluded Caribbean cove is hailed by the Guinness World Book of Records as the planet's brightest bioluminescent bay. It glows due to the high density of dinoflagellates - microscopic plankton that dramatically come alive when disturbed. We'll be kayaking on the bay - once we've slathered ourselves with insect repellent.
"Don't put your usual DEET on," says David, our big, friendly bear of a guide. "No chemicals are allowed in the water. Use this instead." He hands us a can of DEET-free spray, insisting it'll deter the mossies, while helping to preserve the bay's pristine environment.
Accessible via a bumpy dirt track, 3km from the traveller-friendly beach town of Esperanza (where David collected us in a quirky old yellow school bus), Bio Bay is the most talked-about attraction on an island that's enjoying a visitor renaissance after decades in the tourism wilderness. From World War II to 2003, the US Navy occupied two-thirds of Vieques for bomb testing and military exercises until a community-led campaign persuaded the generals to take their war games elsewhere.
While showing us how to navigate the glass-bottomed kayaks, David switches effortlessly from American-accented English to rapid-fire Spanish (bilinguality is common in Puerto Rico, a former Spanish colony, long-time US territory and popular launchpad for Caribbean cruising). We're in Vieques after a seven-day Caribbean jaunt with Celebrity Cruises and are joined this evening by a young French couple and a few vacationing families from the Puerto Rican 'mainland'.
What strikes us first about Bio Bay is not the water which, from the shore, looks dark, still and unremarkable, but the racket from the surrounding mangroves. "Crickets and coquis," says David, explaining the latter is a small frog native to Puerto Rico that's renowned for its high-pitched mating call. The trilling continues as we float out into the blissfully tranquil bay which, according to Gabo, David's equally loquacious colleague, got its name not from any malaria-spreading flies, but from 'El Mosquito', the boat of Roberto Cofresi, a Puerto Rican pirate regarded as a Robin Hood-like figure in the Caribbean.
This robber-of-the-rich-giver-to-the-poor would use this and other bays to elude the authorities (he was eventually captured, though, and executed by firing squad in 1825). Hidden to us initially, the bay's magic reveals itself as we paddle. "Wow, it's like stirring a magic potion," says my partner, Celine, as a bluey-green glow illuminates the darkness beside and beneath us. The dashing flecks visible through the bottom of our kayak reminds me of the green 'digital rain' from the movie, The Matrix. Celine, a Harry Potter fan, reckons it's like something out of Hogwarts.
"Put your hands in," says Gabo. As we twirl our digits through the water - which is almost as warm as the air temperature (30C) - luminous finger-shaped shadows appear, vanishing a second or so after we withdraw our hands. Centuries ago, the island's indigenous Taino people and early Spanish settlers believed the glow was the product of supernatural phenomenon or black magic. But it's the dinoflagellates, called pyrodinium bahamense (or 'whirling fire'). Scientists estimate there are about 160,000 per litre of water, and they thrive thanks to the decomposing, nutrient-rich mangrove leaves that germinate the bacteria they feed on.
Bio Bay shines year-round, but it's best at the start of the New Moon, when the skies are darkest. We're here two days before the Full Moon, but we're lucky, and not just because it's overcast tonight. "We don't run tours on the day of the Full Moon - or the day before or after it," says David.
Bio Bay isn't the only exhilarating draw on Vieques. This Spanish Virgin island (population: 9,000) boasts some of the most unspoiled (and empty) white-sand beaches we've stepped foot on outside of Australia. From our base in Esperanza, we stroll to Sun Bay, a 3km-long cove lapped by serene, turquoise, bath-tub warm waters. After a dip, we laze under coconut trees with cocktails from the rustic beach cafe, with Celine exclaiming: "This is probably the best pina colada I've ever had!" The national tipple, pina colada was 'invented' in Puerto Rican capital, San Juan, in the 1960s.
On neighbouring Media Luna bay, we eye a photogenic couple modelling on SUPs (standup-paddleboards). The next morning, we hire bikes from an affable Esperanza tour operator, who traces his family tree back to Roberto Cofresi. Pedalling a string of quiet, mildly undulating and well-surfaced country roads, we pass derelict sugar mills and dozens of half-wild Paso Fino horses.
These peaceful animals roam freely on Vieques and you'll often see them grazing on grass and chilling out with herons. Entering the former military perimeter, now a wildlife reserve - albeit with restricted areas riddled with unexploded bombs and hazardous material - we pause at Playa Caracas, or Red Beach (most beaches have their original and 'navy' names).
Apart from a couple of picnicking Puerto Ricans, we have 'Caracas' all to ourselves, and about 100m offshore we swim with schools of technicolour fish ("It's like an aquarium!" says Celine, her masked face bobbing above the water). It was Vieques' diving-and-snorkelling-friendly coral reefs that inspired the surreal architecture of El Blok, a new boutique hotel in Esperanza.
It's a hip, Brutalist alternative to the cosy family-run guesthouses that sprinkle this sleepy, easy-going town where, by day, old-timers play dominoes in the shade, and at night (particularly at weekends) revellers of all ages congregate in open-air bars that boom out salsa, merengue and reggae. Next to El Blok is El Quenepo, an 'island-casual' fine dining restaurant bigged-up by the New York Times (local fishermen provide fresh seafood for specials like pan-seared mahi-mahi and spiny Caribbean lobster).
At nearby Duffy's, an Esperanza institution (founded: 1969), you can feast on stonking great Angus beef burgers, American craft beers, and lots of rum. You might bump into Donna Duffy, a mine of information about Vieques (she recommended us the little museum next door; it has interesting displays about Bio Bay, the navy occupation and the island's eco-tourism ambitions). Fittingly, Esperanza means 'hope' in English.
Another perk of visiting Vieques is the flight over. It's just 20 minutes from San Juan in a tiny eight-seater plane, but the window views - all lush rainforests, jaw-dropping coastline and crystalline seas - linger long in the memory.
Two-hour kayak tours of Bio Bay cost US$50 with JAK Water Sports; jakwatersports.com
Hire bikes from Esperanza-based Adventures Bieke Caribe from US$15 per day; biekecaribe.com
El Blok in Esperanza has rooms from US$140; elblok.com
Close to Vieques' airport, the sleek W Retreat & Spa has rooms from US$294; wvieques.com
Qantas and American Airlines fly from Sydney to San Juan via Dallas. Vieques Air Link fly to Vieques from San Juan's international airport, and the smaller 'Isla Grande' airport, a stone's throw from San Juan's cruise terminal; viequesairlink.com
Celebrity Cruises runs dozens of cruises from San Juan between October and April, including 7-day Southern Caribbean cruises, priced from AUD$979. Itineraries vary depending on dates, but St Thomas, St Maarten, Dominica, St Lucia and Barbados are some of the islands visited; celebritycruises.com
Steve McKenna was a guest of Celebrity Cruises (but paid for his own trip to Vieques)