Think large ship cruises are a snooze? You haven’t sailed lately on the world’s most exciting mega-ships. Each one is virtually a floating city with a world of attractions, activities, Broadway-style shows, luxury spas, shopping, specialty restaurants, and even on-ship breweries. The biggest ships are now raising the bar to one-up one another to offer unique experiences to make cruisers forget all about boring pastimes like on-deck shuffleboard. Here are four of the most exhilarating thrills at sea.

Crystal Cruises sails the Crystal Esprit, a 62-guest yacht that travels with its own mini-submarine. Lucky guests can take 30-minute underwater excursions in the submersible vehicle on the Adriatic Coast in spring and summer, and near the Seychelles islands in winter. The petite glass capsule holds two guests and a captain.

Disney Cruise Line wins accolades for offering the first elaborate water slide on a cruise ship. Designed by Walt Disney Imagineers and built on the Disney Dream and Disney Fantasy ships, AquaDuck is a one-of-a-kind water coaster where riders slide through a translucent tube, careening over the side of the ship then taking fast dips, turns and uphill swoops, all while taking in a fun story of Donald Duck and his nephews Huey, Dewey and Louie.

Norwegian Cruise Line hits the gas with the world’s largest go-kart speedways at sea on its three newest mega-ships, the enormously entertaining Norwegian Joy, Encore, and Bliss. Pursuitist buckled up for the ultimate wild ride on the Bliss, covering 1,000 feet of bi-level, indoor-outdoor track in a tricked out electric kart with a headrest blasting Formula 1 racing sounds. Each track has 10 cars with a boost button that can be used once per lap for extra zip. The eight hairpin turns make the competitive, 10-lap race feel much faster than its 30 MPH max speed. No driver’s license required.

Royal Caribbean takes cruisers for a thrill ride on 100-foot-high, 10-story tubular slide. Billed as the world’s “tallest slide at sea,” the Ultimate Abyss takes thrillseekers on a 13-second, LED-lit ride with a 420-degree corkscrew and 360-degree turns. Free aboard Harmony of the Seas, Symphony of the Seas, and Oasis of the Seas.