Like turds in a pisspot,' says a cadet, musing on the ships crammed into Weymouth harbour. I ignore him. Although the saliva is still drying on my cheeks from so many Polish welcomes, if the wind were suddenly to change now my expression would be stuck in one of fear.

I am on the Dar Mlodziezy, a square- rigged, three-masted vessel, one of 34 contestants in the first leg of the Cutty Sark Tall Ships Race, from Weymouth to Corunna in Spain. On board with us are 120 Polish sailors. The woman with whom I am sharing a cabin has already taken off her wedding ring - to prevent it chafing on the ropes. All my years watching the American TV programme Love Boat could not have prepared me for this, and I have forgotten to learn the Polish for 'OK if I just watch?'.

However, just watching is how I seem to spend most of the first day. The deck is pale and clean, but I have to look down constantly to avoid stepping in coils of orange rope steaming in the sun. The massive canopy of white sail billows silently above. The crew are all officer cadets on a training voyage from their academy in Gdynia, and in their safety harnesses they look like unattended toddlers.

In turn, the cadets warily eye us, the small group of paying passengers. I don't blame them. While we are drilled on how to get into our Mr Blobby-style survival suits, I look around and realise that we resemble a typical Agatha Christie cast list. There is a German plastic surgeon and his remodelled wife, who has a face that looks like a tight bag of walnuts and radioactive Twiglet hair; on their third tall ships race, they are obsessed with their video camera, which keeps focusing with a fatal attraction on a British photographer, an 80-year-old war veteran.

Even more sinister is Jean, a French ship-spotter dressed in red anorak and cords. He has the hairstyle and beard of a fanatic and believes that if he stops recording the minutiae of the ship's motions in his little red notebook, the Dar Mlodziezy will sink. By the time soup is sloshing in the tureen at dinner, my motive for murder is plain: Jean has jabbed a greasy spoon at my face and noted that I have 'the bootiful lips'.

It is a relief to be up on deck to see the start of the race, with so many tall ships cleaving through the sunset waves. We watch in silence as we make for the start line, effortlessly ahead. But then I begin to notice the crisp packets and the other gently shimmering rubbish in the water, giving the English Channel the appearance of a huge park boating pond. Suddenly Jean is at my side, and I have a nightmare hallucination of a leviathan French head peering over the horizon, crazed at the remote controls of our boat.

To ease my nerves I see the chief officer about joining a watch. The hierarchy of the ship is established in terms of facial hair, and I am speaking to a large moustache. 'I will give you first watch, but you will not like.' 'Oh, I'll like,' I say, wanting to appear hearty. He smiles.

The first watch comprises about 30 cadets on duty from midnight until 4am, then midday to 4pm. I arrive under the bridge when the midnight whistle blows for the watch changeover and I can see immediately what he means. The third watch look like clean, fun-loving guys; all you can see of the first watch in the darkness are black hulks with shaved heads and glowing fag butts. Their safety harnesses clank menacingly. The first watch's duty for half the night is to peel the ship's supply of potatoes, and, as the whistle is blown, three sacks are tumbled on to the deck, making a potato mountain, lit blue by the moon.

The watch hunkers round the potatoes in a circle, cursing. The bos'n has an anchor tattoo and seems to introduce himself as Popeye. When he leaves, a cadet called Tomasz fetches his guitar and it is only after hearing the whole Nirvana back catalogue that I realise he is not singing in Polish. The others circle him admiringly, potatoes forgotten, and I start to attract attention by being able to decipher a tape of some of Kurt Cobain's more drug- slurred lyrics. Some of the group begin to slope off, trying to sleep in the shelter of small doorways, 'like Romanians in our country', says Tomasz's skinhead friend, Honda. Soon, I join them.

I wake up next day lying alongside my bunk, on the side of the ship. It has begun to rock: I lurch drunkenly up to the bridge, only just in time for the midday duties. First watch is cleaning the white, bony-hipped sides of the ship. Instead of saying hello, the cadets have a curious greeting in which they blink both eyes at me, like cats. Opposite me, blinking and scraping a ladder, is Piotr. Like the others, he is huge, with fat brown sausage fingers, but has the look of an overgrown boy, in shorts and zip-up jacket. His father is a physicist in Gdansk and never wanted him to join the merchant marine, but Piotr assumes the air of a Conrad, thrilling me by fixing my eye and saying: 'I am running away.' Disappointingly, I later realise he meant from Popeye.

By dinner-time of day two the mess is a scene of squalor. In the pitching room, vomit and food fly. This is apparently mild stuff. Piotr says they had to clean the sails on an occasion when his nauseous friend went aloft in a Baltic squall. Jean entertains the incapacitated with his lists of radar bearings.

I escape to potatoes, and afterwards a much-depleted first watch led by Honda performs a punk cancan on the rolling deck, with Tomasz providing guitar accompaniment. What good husband material these cadets are: experienced potato peelers and very stylish in sailor outfits with the bondage harnesses. I am unable to continue this pleasant line of thought: the heaving black sea rushes towards my face, the line-up nearly loses a dancer, and I decide it is time to turn in. Down below, while peeling potato off my thighs, my head smashes against the wall; and all night I have to hug my bunk, which slopes jokily floorwards.

Despite the waterfall of vomit down the central stairs for these first mornings, after a few days everything is quiet. Sufferers start to find their anti- nausea bands and patches more useful as hangover cures. Eventually, we are becalmed. The huge sails flap and twitch like suburban curtains. In the first watch's humid communal cabin, the atmosphere is that of a prisoner-of- war hospital. Piotr has an eye infection and groans on his bunk in the half light. All their chess sets lie unplayed. Through the porthole we can see the Russian ship Kruzenshtern mysteriously overtaking us on the airless waters, while our ship swings in senile circles. The crew accuses it of using the engines and renames it Dieselstern.

On deck, the only sound is of the ship's master's son restlessly lassooing the railing. Popeye solemnly gathers us round while he throws his best boots overboard as a charm for wind. They sink dead in the glassy calm. He tells us the most potent spell for wind is for a virgin sailor to touch the main mast; but nobody is volunteering, not even the cherubic Piotr. On night watch the ship is spectral, haunting the sea. The sails are ghostly moonlit, and pull in their wake a birdless silence.

One or other of the charms soon works, but as the wind picks up, so, unfortunately, does the exuberance of the watch. For five days I have been trying to avoid it; now they insist it is time I go up the rigging. So, feeling even more like a little sister dared by the big boys, I run and ask the first officer for permission to be trussed in my harness.

Piotr tells me to climb. I'm not sure I want to do this. At first it is easy, but the higher I get, the more exaggerated the ship's tilt becomes. One moment I am violently lurching back over the Bay of Biscay, the next having my cheeks forced through square rope holes looming above the upturned faces on the deck.

By the time I haul myself over the second platform, Piotr and I have been through a definite bonding experience. My harness is strapped to his and, squashed in the shaft of cables and ropes, I am partly hugging him with relief, partly unable to stand. I didn't realise how high we were; now, grinning and saying 'Wow]', I am astounded by the blast of space, light and wind. I check a hysterical impulse to fly the 90 feet down to the deck.

Despite my exhilaration, Jean's mood has turned nasty. That night at dinner he reconstructs the fall that did not take place, using dumplings and a bottle of ketchup.

I have now spent a week arguing with Honda. He is still trying to convince me that the cadets' home town of Gdynia is not an industrial smokestack but 'the LA of Eastern Europe'. Together we are listlessly painting an engine vent that always smells of hot-cross buns, so anything seems more important than that. Suddenly, everyone is shouting. 'Delfin]'. We hurtle to the rails in time to see three glossy-backed dolphins break out of a wall of water, then hoop up over a wave.

That night in the cabin we celebrate with some Cutty Sark, and a game of Macao. They warn me that Poles cheat as well as they drink, but I am not prepared for eventually having to abandon the game because most of the pack is hidden in cadet orifices.

On watch, I feel oddly at one with the potatoes, and my knife cuts as though through butter - even if the end product is no larger than a Malteser. Lying back, looking up, the pyramid of sail lit blue and red by the night lights reminds me of a Zoom ice-cream, and of how little I miss the pleasures of land.

A homing pigeon from Grimsby lands on the ship; and, next morning, after eight days at sea, we sight the northern-most tip of Spain. The Germans reappear with their video as we clean the deck. The girls are victimised by a large man with an industrial-size seawater hose. I go drenched to my cabin to change, nursing my 'potato finger', which is raw from clenching the knife.

Meanwhile, the cadets change into their uniforms, dazzling white in the Spanish sun (except for the one worn by an unfortunate who had washed his along with a pair of red socks). Travelling in the real time of a ship is strangely unsettling: instead of feeling you have arrived too early, as on a plane, you expect never to arrive at all. It is surprising, and sad, to see the finish line outside Corunna so soon.

When we land, our legs buckle with the sheer solidity of Spain. We are quite drunk on the expanse of open spaces to roam and roll, deckless and reckless. Piotr leaves us to buy an Airfix plane. The bars serve clear spirits out of unmarked bottles, and soon I feel in need of a comforting ship's railing, but I press on, treating the group to my theories on the eroticism of uniform.

The cadets stare at me in open- mouthed horror. I begin to think I have violated a naval taboo, until I realise my chin is red with blood: a combination of scurvy and neat alcohol has cracked my lips.

There is a crew party in Santa Monica park that night, a combustion of alcohol and testosterone. By the time we get there, the crews from all the ships (including some with all-female crews) have already drunk it dry and are sucking at each other like fish out of water. My theories (and the Polish saying that 'there's a queue of women behind every uniform') are proved true. We meet an English girl, Lottie, who says she has just been snogging her 22nd bumfluffed Russian sailor. Hopeful Poles hang round the bushes like constipated dogs.

Back on the ship at curfew we gather on deck in the dark, much damaged. Tomasz brings out his guitar and the whole watch growls out what I take to be another traditional Polish shanty; it turns out to be 'Smells Like Teen Spirit'. Their eyes are blinking contentedly like cream-fed cats. I shall miss my gentle, sea-hungry Poles.

Before I steal off the ship at dawn to fly home, I go down into the warm lung of the first watch's cabin, packed with snorting cadets like so many berthed dolphins. I say a soft maternal goodbye, wishing them safe of land and girls. My mother always said worse things happen at sea. They didn't.