Most cruise-curious travellers opt for a small ship for their first taste of life on the high seas — but to pop my own cruising cherry, I headed aboard Symphony of the Seas, the biggest cruise ship ever built, and the 25th ship in Royal Caribbean International’s fleet.

If I explain that she can accommodate up to 6,680 passengers — more than the entire population of the tiny seaside town where I live in Northern Ireland — you’ll understand why I felt slightly daunted.

There isn’t a word in the English dictionary to describe how imposing a ship of such gargantuan proportions seems to a cruise newbie as I boarded in Barcelona for Symphony’s two-night “shakedown” cruise, testing out all systems before she enters service.

Boarding felt like entering a stadium rather than setting sail. Once on board, I felt total sensory overload as I wandered, dazed, along the Royal Promenade; a sleek, mall-like arrangement of bars, shops and restaurants.

It’s no exaggeration to say it took two hours of wandering the decks and getting in and out of some of the 24 lifts to locate my stateroom and check in at the press room, where I was directed to download an app to help me navigate the ship and stay abreast of the dazzling array of activities and dining options available.

Originally a Londoner, I’m no stranger to the hustle and bustle of city life. However it’s this which I normally want to escape on holiday, my perfect trip is usually one that starts with switching my phone off.

But as I headed to the Pool Deck for the Sail Away party, a long-established cruising tradition, my spirits lifted instantly. The carnival atmosphere combined with the breath-taking view from the 16th deck as we sailed out of the port of Barcelona, seagulls circling beneath us, was a remarkable experience — and free-flowing prosecco plus Spanish sunshine might also have had something to do with it.

As the sun set, and land slowly disappeared from view, all sense of cabin fever abated. Dressed in my newly purchased dinner-on-a-cruise ship outfit (dressing up is optional on Symphony but it seems a shame not to), by the time I’d enjoyed pre-dinner drinks in the nightclub and feasted on gruyere tart and a warm hazelnut chocolate cake in the main dining room, I was beginning to think I’d got the hang of cruising.

I rounded the evening off with cocktails, made by robots to my exact specification in the Bionic Bar, before collapsing into the enormous bed in my ocean view stateroom.

The next morning, I slid open the door to my balcony, and let the sun warm my bones while the ocean lapped beneath me — perhaps the most sublime start to any day I’ve ever had.

Re-energised, I explored every inch of all seven “neighbourhoods” on board, from the Adventure and Youth Zone — though I wasn’t brave enough to try the zip line or Ultimate Abyss, the tallest slide at sea — to Vitality Spa and Fitness, where a 50 minute Swedish massage costs around £90.

I toyed with the idea of donning my lycra to test out the running track which stretches around the ship’s perimeter, but the call of a caipirinha in the solarium was so much stronger.

The quiet, outdoor spaces were my haven. I loved Central Park, not for its seemingly-endless array of restaurants but for the tranquillity of being outdoors among 1,200 real trees and plants despite being at sea. Piped birdsong felt a bit much though — some things just shouldn’t be simulated.

The real highlight, however, was the thing I’d expected the least of. The entertainment on cruise ships conjures up a certain kind of stereotype — ‘Doris at the Bingo’ was how a friend teasingly described it — but watching Olympic divers and tightrope walkers at the outdoor Aqua Theatre was one of the most memorable performances I’ve ever seen.

I gave the world’s largest casino at sea a wide berth, but the goings-on at the Studio B ice rink, with its video screen frozen into the ice, are truly mesmeric.

That’s before I mention the glorious glamour of a bar that moves between decks (Rising Tide), the eye-popping breakfast buffet extravaganza on offer at Windjammer Marketplace on deck 16, mouth-watering made-to-order fish tacos and the best guacamole I’ve ever tasted at Mexican-inspired El Loco Fresh or the has-to-be-seen-to-be-believed extravagant brilliance of the Ultimate Family Suite — already booked for around £46,500 for a week at Christmas.

The question I’m asked most frequently by friends (after “Can you take me with you next time?”) was whether it feels like you’re at sea on a mega cruise liner like Symphony.

Forget every dodgy ferry crossing you’ve ever known, it’s incomparable. Apart from the occasional ever-so-slight vibration, you can entirely forget you’re on a ship.

I teetered around in high heels without once needing to grab hold of something to stay upright (even after those cocktails), and I didn’t see anyone so much as steady their wineglass at dinner.

Royal Caribbean says Symphony of the Seas was designed to inspire unshakable wanderlust within guests of all ages. From a final dessert of fried cheesecake so delicious that I almost shed a tear, to moments of absolute bliss alone on my balcony, I say: mission accomplished.