The wind is getting stronger and the waves higher. As a sailor I can recognise the brisk little squalls charging across the surface of the sea; if I was in a boat, this would be fun. But I'm in a sea kayak. As it's only 14 inches deep, I'm not so much on the water as in it.
This is the first day of a four-day trip up the west coast of Espiritu Santo Island, just off Mexico's Baja California in the Sea of Cortez, and only my second day of sea kayaking ever. Thankfully we have already practised "wet exits", the art of banging on the hull of an upturned kayak before pulling off the sprayskirt to swim out of the cockpit.
The technique is a useful one; beginners can find an eskimo roll, a common method of righting kayaks, tricky in sea-going models. All the same, I'm relieved when we eventually make it to the beach where we will camp for the night.
"Right," says Leah Blok, the amiable guide responsible for our seven-strong group, "our next lesson will be how to paddle big waves."
The next morning, she gets out a whiteboard and marker pen and begins to explain how and why the safest technique for waves approaching from the side, as they had been the previous day, is to dig in for a stroke on the oncoming face of the waves. This tilts your body into the wave and prevents it rolling the kayak. Then, as the crest passes under (or over) the craft, swing in for a second stroke into the receding backside of the wave, so you are not leaning down the wave.
Though it sounds complicated, it is in fact very simple and, as I discover the next day, effective. Of course, the safest way to approach waves is head-on, because the prow of the kayak is designed to slice through the wave and its sleek midriff guides water around the sides of the craft.
The Sea of Cortez, the narrow but menacingly deep channel of water between the 1,000-mile long Baja peninsula and mainland Mexico, was described by the pioneering French underwater explorer Jacques Cousteau as "the world's aquarium". It is one of the most diverse marine areas in the world, containing 31 marine mammal species (one third of the world's whale and dolphin species), 500 species of fish and more than 200 bird species.
It is also a very fragile ecosystem, under pressure from developers on both sides of the sea. This is why Espiritu Santo, a 23,300-acre island 20 miles offshore from La Paz in the southern part of Baja, was bought by the Nature Conservancy, an international organisation dedicated to preserving ecologically important sites, for $3.3 million (£1.7m) in 2003, when it became a protected area.
Our sea kayaking trip, organised by the La Paz-based outfit Baja Outdoor Activities, run by a British expat, Ben Gillam, and his wife, Alejandra, is as low-impact as possible. For a start, apart from the boat trip over to the island and back, we will be powering our own way up the west coast, converting calories into kinetic energy.
Everything we pack in, we pack out; that means everything. We'll even be using a "porta-potty" - we can't use a compost toilet because the sand has no bacteria with which to break down waste. And we've been asked to wash in sea water with biodegradable shampoo; Leah's dread-locks are starting to make sense now.
The west coast of Espiritu Santo, which means "Holy Spirit", consists of a series of sandy coves divided by rocky headlands, and when we're not kayaking we'll be pitching tents on one of the island's 20 deserted beaches. In our time off we can practise rescues and rolls, go for hikes into the rocky interior of the island or snorkel among the tropical fish, including poisonous pufferfish and stingrays.
If you're a plant on Espiritu Santo, it helps to be thrifty with water; towering organ pipe and cardon cactuses are common here. The cardon, the world's largest cactus, is pollinated by bats, so it only flowers at night.
With warm water, mild weather and sheltered seas, few winter kayaking destinations can match Baja. But this is not an entirely benign stretch of water; last year a female decathlete died as she was attempting an eight-mile open-water crossing in the Sea of Cortez. When the weather turned nasty, she capsized and stayed under the cockpit for shelter while radioing for help.
Fishing boats scoured the area looking for her but couldn't spot the white hull of her kayak among the whitecaps. The searchers listened and talked to her for 10 hours, until there was silence.
"Sea kayaking requires that you think about currents and wind, and you need to take much more notice of the weather forecast than if you're going out on the local lake," says Leah. But the 5ft swell that we master on our first day gives an indication of what sea kayaks, in inexperienced hands, can handle.
Leah, who learned to kayak in the icy waters of British Columbia in Canada, has kayaked in 10ft waves and covered 28 miles in a day; we paddled four miles on day one.
In the first light of morning - bedtime is determined by when the sun sets and rises - pelicans line up in the blue sky for breakfast, plummeting into the bay one after another like a squadron of Stuka divebombers. Look closely and you can see them turn their heads sideways at the last minute to protect the oesophagus and windpipe.
Day two begins with a six-mile paddle to Candel-ero and Musteno beaches, two of the most attractive on the island. We're a disparate group; while it is the first time in a kayak for a Washington lawyer, a couple from Oregon keep a tandem kayak in their garage. But Leah manages to keep us together on the water. Despite my mild aquaphobia, with every stroke I appreciate the pleasure of paddling more; it's all I can do to not race off towards the horizon like a clockwork toy.
As we surf into the bay with the tide at the end of the day I can see stingrays gliding along the sea floor and there is a deep silence, apart from the gurgle of water under my bow.
There's an art to kayaking, and stringing a series of perfect strokes together brings the same joy as surfing. "Use your back and abdominal muscles to move the paddle through the water by twisting the body on each stroke," instructs Leah. "You'll tire very quickly if you just use your arms and shoulders.
"Grip the paddle but don't clench it. Pushing the upper end of the blade away from you is more effective than just pulling the lower end through the water.' Steering is by foot-operated pedals, which turn the kayak's rudder left and right, although the more stylish exponents control direction with their paddles. Buoyancy comes from two chambers (fore and aft), and confirming that the neoprene and plastic covers of these are closed is part of the morning's pre-kayaking checks.
As we kayak north, seeking shelter behind Isla Gallina, Isla Gallo and Isla Ballena, we give the headlands a wide berth: this is where waves rebound off the cliffs to create a choppy area of water. "Clapitus" is the technical term; "soup" is the descriptive word our guide uses.
The longer a kayak, the faster and more stable it may be in rough seas; my 17ft fibrelass Seaward Tyee is a middle-of-the-road model, but enthusiasts will spend thousands on sleeker, carbon-fibre kayaks. Our average speed is two miles an hour, although Leah has covered 11 miles in two-and-a-half hours, wind- and current-assisted. Later this year, when she takes on Ben Gillam's record for a one-day circumnavigation of Espiritu Santo, she will need to paddle 40 miles in a day.
Our final day brings the biggest test, a two-and-a-half-mile open-water crossing between Espiritu Santo and the smaller Isla Partida, where a sea lion colony will provide the afternoon's entertainment. After just three days I might not yet be totally comfortable in the water, but I'm confident enough to relish the challenge of the crossing, and attack the bigger waves.
The discovery of Baja California in 1536 was the conquistador Hernan Cortez's last great adventure, but I think I will be back for more.
HOW TO GET THERE
Flights to Los Angeles with Virgin Atlantic (virgin-atlantic.com) start at £284 for bookings by 23 January. Transfers to La Paz with Alaska Air (alaskaair.com) from around £90.
A four-day kayaking trip with Journey Latin America (journeylatinamerica.co.uk; 020 8622 8491) around Espiritu Santo Island costs from £263 per person. Price includes guides, equipment and all meals. Departures in 2007 from January to May inclusive, October and November. To organise your own trip with Baja Outdoor Activities: 001 52 612 125 5636; kayakinbaja.com