Oh, and a glow-in-the-dark laser tag arena that Royal Caribbean says is the largest at sea.

“We set out to create a new level of vacation adventure and deliver the ultimate escape for families of all shapes and sizes,” says Michael Bayley, president and chief executive officer of Royal Caribbean International.

The company also owns the runner-up ships in the size category: Harmony of the Seas, which was launched in 2016, is the same width and length. But it has a gross registered tonnage – which measures the volume of enclosed space on a ship – of 226,963 versus Symphony’s 230,000. In other words, Symphony has more stuff.

“This phenomenon of having these escapist on-board activities that nobody else has, has been going on for a few years,” says Maggie Rauch, director of research for travel and hospitality research firm Phocuswright. Cruise companies are trying to dazzle new guests as well as get repeat cruisers to open their wallets wider on board.

Some of the new ship’s most lavish features are aimed at its smallest guests. The 1,346-square-foot Ultimate Family Suite has a slide that runs from the kids’ room to the living room, a wall devoted to Lego play, a wraparound balcony with a kid-friendly pool table climbing feature, a full-size hot tub, and a theatre-style TV room, complete with popcorn machine and multiple gaming systems.

Royal Caribbean hasn’t announced the price of the two-bedroom suite yet, but says that it can accommodate eight guests. (Rauch points out that one fancy suite may not make much money for Royal Caribbean – but it might be social-media gold. “If a family is posting videos of their kid sliding down from their bedroom into the living room, that is free marketing,” she says.) It also comes with a dedicated Royal Genie – the cruise company’s version of a private butler.

The Genies are human, unlike the bartenders who will be working at the Bionic Bar, already a fixture on Royal Caribbean’s three other Oasis-class ships. Made by Italian firm Makr Shakr, the mechanical mixologists can muddle, shake, strain, and serve cocktails made from any combination of 30 spirits and 21 mixers. (The robots work in pairs and on other ships have such names as “Mix” and “Mingle” and “Shaken” and “Stirred.”)

Royal Caribbean is also giving its 10-storey Ultimate Abyss slide a repeat performance. On Harmony of the Seas, guests ride a mat down the sculptural purple tubes. On Symphony, it will end on the Boardwalk – one of the seven “neighbourhoods” that break up the immense ship.

The ship will feature beefed-up live entertainment, reviving its at-sea version of Hairspray and adding Flight, a Royal Caribbean original about the history of air travel. A new high-diving and acrobatics show will make its debut at the open-air amphitheatre. There’s even a hi-tech ice-skating show. That’s in addition to the 20-plus restaurants, comedy club, watersides, surf simulators, zip-line, mini-golf course, and more.

Symphony will spend the summer cruising the Mediterranean; in November it will move on to Miami, its base for weeklong trips through the eastern and western Caribbean.

Cruisers should find a smoother boarding experience, too – Royal Caribbean will let them check in and upload a selfie to the brand’s new mobile app, then go straight to their cabins after passing through security. Finding their way off might prove to be more difficult.