The River Clyde, Fair Fortnight three days old.

Fair Fortnight, when old Glasgow hung its bunnet on a shoogly peg and stuffed its hairnet in a drawer. Two weeks were theirs, theirs away from bosses and the tyranny of steaming chimneys.

With the slam of a tenement door did the chains peel off for a fortnight. Most headed for water - the ferry home to Ireland, the charabanc and train to a loch or, best of all, a paddle steamer "doon the watter". Such frothing beasts pounded their way over the Clyde and deposited fair fortnighters at Helensburgh, Rothesay and Largs. Their boarding houses awaited. Some still take off these first weeks of July, tied to the tradition, if not the shipyard or the factory.

It is Fair Sunday, and all of us - old men and women who remember those bunnet and hairnet days, their children wondering when it is acceptable to open canned beer and handbagged voddie, their grandchildren playing games on tiny screens - are going Doon the Watter for a day, an expectant army marching on bacon rolls. "This vessel replaces the Clyde steamer Waverley which was built in 1899, served as a minesweeper in the 1914-18 war and was sunk by enemy action at Dunkirk in 1940," reads a plaque in bold brass, this country as ever stalked by history.

Wooden walkways, benches and walls are sharply varnished, the funnels dusk red and a crew busy about dressed all in white like functional angels. It is a black and white experience in full HD. The boat hammers up a surprising tempo, chugging and clanking us out of Govan and through Clydebank, spaces and cranes. "Roast dinners will be available on a self-service basis, that's roast dinners on a self-service basis," crackles the tannoy. The Clyde fattens and the countryside runs wild, mountain peaks and untroubled islands.

Some passengers snooze propped against funnels, others pursue the age-old battle between broadsheet Sunday newspaper supplements and the wind. Couples rub noses, gangs huddle in the bar. Another set of people look out to the water and shake their heads with half a smile, remembering. It seems like a celtic "thin place", not one where heaven feels closer, though: one where we can feel the breath of the past against our necks.

"Apparently there's a special word for the feeling you get when you've left your mobile phone at home," says a bloke in his 60s, peering up from his Sunday Times. Gradually the Clyde becomes more like the ocean and the air moistens. Two women in sunglasses pinch their hoods tight to their faces. "Will we go inside, Susan doll?" "Aye. It smells a bit 'seaside' now anyhow."

The wind rises and more people follow them, most to one of three bars. It seems half the fun of going Doon the Watter is missing going Doon the Watter. There is an attractive ambivalence to hiding in the dark hull of a ship while Scotland puts on a show. It suggests a knowledge that she will always be there for people when they need her, but photos and maps are for tourists. To go Doon the Watter is not an act of vacation, but an act of ritual.

For most of the journey, a commentator tells people what they would be seeing were they looking outside the boat. He stands behind a funnel, a plastic bag filled with scraps of paper and local history pamphlets for that moment when a year or name slips by him.

Sadly, his words can be heard only in between the sea gale. It is like drifting in and out of consciousness during a school geography lesson. There is more schooling in the engine rooms, where dads and their sons and daughters point at whooshing pistons and draw pictures on pads bought from the souvenir counter.

On the shore, blinking lights, the faint rhythms of fairground music and the elegant art deco edges of Nardini's ice cream parlour mean we have reached Largs. The boat hums its way into the harbour and the gangways are lowered. 'I feel FREE," says a girl in her late teens as our shore leave begins. "Aye, they were the worst people ever, like," replies her boyfriend. The seaside streets lack people: most are in Nardini's.

Among reassuring décor, booths and wooden partitions, waiting staff hover around balancing trays of vivid treats and fish 'n' chips. There is a pianist in the corner, but his velvet tinkling is out-muscled by chitter chatter and laughter. Every drink still legal can be had here, but no-one is on the booze. It's a teapot or milkshake kind of place, a glass bottle of Coke or hot chocolate one. The two tables nearest us sum up the wonderful universality of this place: on one, two pensioner blokes contentedly ignore each other while reading the Sunday papers; next to them, a lad and lass of no more than 15 years old sip from strawberry milkshakes, nervously falling a little bit in love with each other.

On the Esplanade, between palm trees and a giant sculpture of a Viking warrior, families eat picnics. The beach has a smattering of folk hobbling over its cobbles. There is more colour yet in Beachcomber's ice cream, hot dog and candy floss stall, everything soundtracked by arcades. Inside these multi-noised meccas, grannies bet 10 pence, and a gang of young women dance around screeching like worries are things that happen somewhere else. Slot machines called Disco Fever and Salsa flicker away, and children put all the pressure of their young hearts on their dads to pluck a win from the grabber machines.

By "the shows" - Kiddie Kastle, Krazy Kars and a set of trampolines whose sign asks participating bouncing toddlers to "remove all sharp objects and coins" - we sit by an old man on a bench. "It never stops, does it," he says fondly, shaking his head. "It never changes."

Extracted from This is Scotland: A Country In Words And Pictures by Daniel Gray and Alan McCredie, published by Luath Press, £9.99

The authors travelled doon the watter on the paddlesteamer Waverley www.waverleyexcursions.co.uk