Cruise holidays are the epitome of relaxation, but sometimes a dash of adrenaline is needed to liven things up – and major liners certainly aren’t short on unique, exhilarating thrills.

From waterparks with double-loop slides to vertigo-inducing rock-climbing walls and even tightrope walks high above the top deck, a growing number of cruises are pushing the boat out with a variety of thrill-seeking amenities on board.

But Norwegian Cruise Line’s ship, Norwegian Joy, boasts a heart-racing attraction that stands out from the rest – and it happens to be a world first.

Out in the middle of the ocean, guests can climb into go-karts and zip around at speeds of up to 35mph on the vessel’s two-level track, Speedway.

The world’s first go-kart track built directly on top of a cruise ship features sharp bends and technical turns, offering an adrenaline-fuelled experience for families and guests of all ages aboard the sprawling 3,804-passenger vessel.

In a new YouTube documentary, Ship Shape, the Daily Mail goes behind the scenes of the impressive liner and takes a look at the various high-adrenaline activities on offer – from the one-of-its-kind go-kart track, to a private island with two huge zip lines.

On Norwegian Joy, the world’s first go-kart track built directly on top of a cruise ship offers guests an exhilarating opportunity to race above the see on a two-level circuit 

Racing around above the sea with nothing but open water and sky around them, the go-karts are powered by electricity, allowing them to be stopped quickly and safely should a malfunction occur or if a rider needs to exit the track.

Should riders wish to overtake, each steering wheel is fitted with a ‘boost’ button that offers a short burst of extra speed.

Each ride lasts around eight minutes and is available for both solo and double riding.

The go-kart is just one of several lively attractions aboard the £640 million Norwegian liner, which first launched in April 2017.

It joins the likes of an open-air laser tag arena, a virtual reality pavilion featuring simulators such as hovercraft bumper cars, and multi-storey water slides.

When venturing off the ship, guests can explore Great Stirrup Cay in the Bahamas – the first island ever owned by a cruise line. 

Previously used by pirates as a hide-out, the 268-acre idyllic island is home to two zipline routes called Osprey and Seahawk that join to a tower overlooking the endless rows of sun lounges on the white sandy shores. 

Darren Hreniuk, founder and president of the Original Canopy Tour, installed both of the ziplines.

On Ship Shape, he reveals, ‘There are a lot of people who come here, it’s funny, sometimes you’ll get elderly people that come and it’s on their bucket list and they don’t care they’re just going to do it no matter what, they’ve lived their life and they just go “yee-haw”. 

‘And you get some young people who are really used to athletics and what not, they get on and their knees start wobbling and they sort of get paralysed.’

Each kart reaches speeds of up to 35mph and is fitted with a boost button, allowing riders to overtake

Private island Great Stirrup Cay is home to two zipline routes called Osprey and Seahawk that join to a tower overlooking the endless rows of sun lounges on the white sandy shores

Back on board, there is the first ever double looping waterslide on a cruise ship – the Ocean Loop – that hangs over the edge of the boat, as well as a floating water park and a beach club. 

After a day of adventure and adrenaline highs, the ship has a spa perfect for relaxing  – the award-winning Mandara Spa.

Hannah Marsh, assistant spa manager, describes to Ship Shape how it is the ‘perfect place to unwind’.

The spa boasts the largest thermal suite out of all of NCL’s ships and is lined with floor-to-ceiling windows offering sweeping views of the ocean.