Carnival Horizon: Carnival's newest cruise ship, where having a good time is taken pretty seriously

"Choose Fun" says the sign held up by the smiley check-in staff of Carnival Horizon, the 26th – and newest – ship in a fleet that takes having a good time pretty seriously. Indeed, as we step on board, into an atrium lobby that soars three decks, with a buzzy bar wrapped around a giant whirlwind-shaped LED screen, surrounded by cocktail-sipping guests (from twenty-somethings to pensioners) shaking their hips to pumping dance music, my other half whispers in my ear: "Can you feel the fun?" You certainly should when cruising with Carnival. This, after all, is a company that has appointed basketball legend Shaquille O'Neal as its CFO (that's Chief Fun Officer). It's Shaq's job to spread the word, in adverts and media appearances, about the joys of a Carnival cruise, where the daily on-board newsletter is The Fun Times, the entertainment team the "Fun Squad" and countless activities and shows – from Harry Potter quizzes and Dr Seuss-inspired water slides to Lip Sync Battles and hairy chest contests – are designed to raise a smile from even the biggest Grinch. So, just how "fun" is Carnival Horizon? And is it possible to escape the merriment every now and then for a bit of peace and quiet?

VISTA'S SISTA

Like its same-same but slightly different sister (or "sista") ship, Vista, which launched in 2016, Horizon can carry 3936 guests at double occupancy, plus 1450 crew. Most passengers – and some senior staff – are from the USA, but there's a genuine international flavour, with couples, families and groups of mates from across Europe, Asia and Australia on our seven-night Mediterranean cruise from Barcelona. There are also seven crew members from Down Under, an Italian captain, chefs, waiters and stateroom attendants from nations as varied as Serbia, St Lucia, Thailand and Colombia, and a British cruise director, Mike Pack. A bundle of energy, Mike directs many of Horizon's fun and games and as we depart Barcelona, with Sardinia, Naples and Civitavecchia (Rome) among the ports of call on our itinerary, he's orchestrating a sail-away party on the wide, tenth-floor Lido deck as a DJ spins a string of singalong tunes. Preferring to observe rather than participate, we enjoy the rather surreal spectacle of (mostly adult) passengers conga line dancing with costumed staff dressed as Dr Seuss characters as the sun-kissed Mediterranean Sea twinkles in the distance. It's a vivid reminder that, while Carnival's ships are famously family-friendly – 800,000 kids sail annually on them, more than on any other cruise line, apparently – you're never too old to join in the party.

SEUSSIAN SPLENDOURS

The activities themed on the whimsical stories of Dr Seuss – the late American author Theodor Seuss Geisel – entertain both the young, and young at heart. As well as Dr Seuss Bookville – a brightly-painted, quirkily-furnished indoor children's play zone – Horizon has Dr Seuss WaterWorks, a splishy-splashy outdoor area where you'll get soaked by huge, tipping hat-shaped buckets of water and ride serpentine waterslides. The "funnest" ones – open to those more than 42 inches tall (106 centimetres) – are the red-and-white-striped Cat in The Hat, which sends you down on an inflatable doughnut tube, and my favourite, the faster blue one, Fun Things. Lay on your back, arms folded behind your head and legs crossed at the ankles, and you'll bullet down in what feels like five seconds (but is probably double that), emerging at the bottom with a fast-beating heart, a silly grin and hopefully with your drenched swimwear still intact. Also on the ship's upper decks is SportSquare, which provides plenty of "dry" entertainment during our cruise (particularly on our day at sea). We play nine-hole mini-golf, fussball, ping-pong, Poly Pong (a specially-designed table for four players) and SkyBilliards (a cross between soccer and pool). There's also Twister, shuffleboard, a basketball court and a jogging circuit (one kilometre is about five laps). If you fancy "cycling" above the sea, join the queue for SkyRide. It's a pedal-powered pod trip on an elevated track suspended above the top deck, and at times, it twists and dips like an old-fashioned fairground ride. Another attraction likely to stir butterflies in your stomach is SkyCourse. You're safely strapped in with a harness, but your legs still wobble as you teeter across planks and ropes perched several metres above the deck. Things get hairier – and more exciting, we find – when the sea breeze picks up.

TRANQUIL TIME-OUTS

Horizon has its fair share of relaxation-first retreats. Serenity, on deck 15, is adults-only, with whirlpool, loungers and shaded beds, while the outer promenades on deck five are usually fairly quiet, too. Indoors, in the lounge-like Library Bar, you can play board games on the chessboard tables, pluck books from the glass cabinets and, for a nominal fee (under US$5), pour a glass of wine from the DIY drinks cabinet. Boasting a public gym groaning with cardio and weights equipment, the Cloud 9 Spa also has tucked-away treatment areas and private aromatic steam rooms that require a special pass. This can be purchased on a daily basis, but is included, along with other spa privileges, if you stay in one of the 104 Cloud 9 staterooms, which range from snug interior cabins to spacious suites. The 79 tropical-inspired Havana staterooms are another standout sleeping option, again spanning various sizes, with the Havana Cabana ones having hammock-adorned balconies. Havana "residents" have a members-only pool by day, though from sunset to midnight, it's open to everyone and you'll see folks drinking daiquiris and mojitos and bopping to live Latino music from the adjoining, beautifully-decorated Havana Bar. A decent compromise, we find, are the Balcony staterooms, which have a retro feel with green, blue, yellow and brown hues, a sofa, desk, TV and king-size bed. Located near mid-ship on deck seven, our room (7823) is nicely positioned away from the main action, but a few minutes' walk to most stuff.