As flying has lost its glamour and budget airlines have made global air travel for the masses affordable, luxury cruise liners have re-emerged as a leading branch of tourism to be worth around £23.2 billion worldwide.

Such is the popularity of cruising that one in eight overseas package holidays taken by British holidaymakers is now a cruise. And, of the 1.7 million cruise trips embarked upon by Britons last year according to the Cruise Lines Industry Association, around 187,000 of those passengers hail from Scotland.

Gone are the days of shuffleboard, minuscule porthole windows and cramped cabins; so too the cheesy stereotypes of TV series The Love Boat or Jane McDonald warbling her way into the heart of the nation on BBC's The Cruise documentary. The attractions are manifold for aficionados: there are the reliable comforts of a floating, luxury resort; waking in a different port each morning without lugging baggage; and the pre-planned excursions that take the hassle out of sight-seeing.

It was Royal Caribbean International (RCI) that led the way in changing the course of cruising from an elite vacation to open it to the mass market through the introduction of amenity-heavy 'megaships', or Sovereign-class vessels, in the late-1980s and early-1990s. The likes of Norwegian Cruise Line (NCL), Carnival Cruise Lines and P&O weren't far behind in the quest for bigger and better vessels that resemble horizontal skyscrapers, complete with climbing walls, shopping malls, ice rinks, waterparks, miniature golf courses and tennis courts. RCI's Oasis of the Seas and Allure of the Seas, the world's largest cruise ships launched in 2009 and 2010 respectively, carry more than 6000 passengers each.

Avid cruise-goer Elizabeth Linnie, from Nairn, Moray, who has notched up 30 cruises, will be one of the first passengers to sail on RCI's next generation of ships, the Quantum of the Seas, which launches in autumn next year. She's booked on a trans-Atlantic crossing from Southampton to Cape Liberty, New Jersey, followed by a Caribbean cruise.

"It's taken over my life," says Linnie, 52. "It's such a fantastic addiction to have, although it can be costly when you really want to cruise so much. I never expected it to be anything like this on our first cruise 10 years ago." That first Mediterranean cruise, on the Splendour of the Seas with her mother Mary Pritchard and son, Alex, now aged 24, paved the way for dozens more around Europe and the Caribbean islands.

"Normally I'd take one or two a year, more sometimes but, for financial reasons this year, we'll save up for next year," she says. "I'm a single mum and it's what our life is: it's what we enjoy and we know that we'll enjoy it when we get there. If you spend your money on a night out, you don't know if the entertainment will be good, or if it will be a good or bad night. On a ship, with the standards that they have, we don't have to worry. We know that we're going to have a great time."

Like many cruise-goers, her trips start long before embarkation. Online forums on allow passengers to discuss their forthcoming adventure before boarding. Linnie founded the International Critters community six years ago, which goes by the motto of 'give something back'. Her charity project on next year's Quantum voyage will raise money for the Make-A-Wish Foundation. For the last three years, the group's members have fundraised to take school supplies, musical instruments and sports equipment to a school in Labadee, Haiti.

ALONGSIDE the mainstream-appeal liners - such as the 1083-ft-long Royal Princess ship launched by the Duchess of Cambridge in June - niche markets have emerged. The ultra-luxury Regent Seven Seas provides all-suite, all-balcony rooms; Viking River Cruises gives a taste of coastal and inland cities; Star Clippers features only tall ships; and Hapag-Lloyd veers off the beaten track with daring expeditions.

Similarly, destinations are broadening in scope: while more than a third of UK passengers chose to cruise the Mediterranean last year, the option to venture further afield - to Siberia, Polynesia, Antarctica or Alaska - is open to more travellers every year, while the launch of China's first luxury cruise liner, Henna, this year is likely to inject more competition into a thriving market. The Cruise Lines Industry Association has reported a 29% increase in travel to northern European destinations, rising to 443,000 trips made by UK passengers, with the Norwegian fjords proving increasingly popular.

Cruise ship visits generated an estimated £41.2m for the Scottish economy last year. This represents 436 cruise calls and 379,955 passengers. Most visitors hail from North America (44.9%), followed by the UK (35.5%) and Germany (17.1%).

Scotland's busiest cruise ship port of call is Orkney with 77 calls and 41,500 cruise passengers arriving into Kirkwall and Hatston last year. Edinburgh came second last year with 76 ship visits and 79,800 passengers through Leith, Rosyth and South Queensferry combined, while Invergordon received 67 calls and 77,100 passengers to the Highlands.

Fred.Olsen, meanwhile, the company featured on BBC2's recent documentary The Cruise: A Life at Sea, charting a 112-night round-the-world voyage, has established a strong Scottish consumer base, with departures from Rosyth and Greenock.

Lanarkshire couple Maureen and John McLean have become more daring in their choice of destinations since they dipped their toes into the waters of the Caribbean on their first cruise 12 years ago. Tired of package holidays, civil servant Maureen, from Wishaw, booked for a western Caribbean trip on the Explorer of the Seas on a neighbour's recommendation - and has now clocked up almost 20 cruises. They have since toured the eastern Caribbean, the Mexican Riviera (which they combined with hotel stays in Los Angeles and Las Vegas), the Mediterranean, and the Adriatic for their silver wedding anniversary.

"You would never in a month of Sundays be able to visit all those countries on holiday. That's part of the attraction," says McLean, 54. "Last year we did Scandinavia and Russia, sailing from Southampton. We thought we would get our own visas for St Petersburg, but it was difficult: you had to organise it here and get a sponsor who had to come and meet you and take you around. It was easier for us to go with the ship's visa and do a couple of organised trips."

Their most unusual routes to date have involved a 14-night cruise of the Panama Canal - starting in Miami, taking in Mexico, Guatemala, Colombia and ending in San Diego - and a cruise from Rome to Dubai, a trip that wasn't without hitch when they missed the boat's departure thanks to an air traffic control strike in Italy. After spending a few nights in Rome, they were flown to Cairo to pick up the ship in Alexandria, from where they sailed through the Suez Canal and past pirates off Africa. "There were watches looking out high up on the mast, and we apparently had armed guards when we were off the coast of Somalia. I thought they wouldn't come near a big ship like ours, but the pirates were there."

The couple credit the loyalty schemes of Royal Caribbean and its sister company Celebrity Cruises for their repeat custom. Earlier this year, they took a trans-Atlantic trip from Puerto Rico - calling at four Caribbean islands and the Azores - to Southampton. Next month, they will tour the Canaries and Azores. "John is every bit as keen as I am. Every time I say 'that looks like a good cruise' he'll just go and book it," says McLean, who counts cruises of Alaska, Hawaii, Singapore and Thailand on her "bucket list".

Their daughter, Gillian, has also been bitten by the bug after taking her first trip with her parents shortly after graduating from university. She has cruised with Thomson and Norwegian Cruise Line, as well as with her parents' favourite companies. "It's the best holiday ever," says the 30-year-old solicitor. "I like the fact that you wake up in a different place every day. I can't lie on a beach; I don't take a tan so I get fed up. Going to all these different places, is so interesting. You have a wee taster of them and then you can go back to places you like on a city break."

The Cruise Show's director Martin Anslow believes it is the diversity of packages that is responsible for swelling cruise demand. "It's the mix between the small ships that take you to places that the bigger ships can't go, and also being able to go to places that you can't visit by land, such as Antarctica or Galapagos or Alaska; the best way to see them is on a boat," he says. "Also, you see a lot of places in a short space of time. For example, you can get a good taste of Europe on a 10-day cruise. To do that by car or train would be quite exhausting."