The new MSC Seaside, which is now sailing the Caribbean from Miami, benefits from an unusual structure that stations the ship's engines and exhaust stacks much closer to the middle of the ship than the rear.
The result is room for a long dual zipline that starts from a platform near the top of the funnel and extends over the back half of the ship to an elevated landing zone overlooking the aft.
The 345-foot ziplines are long enough to make a lengthy wait to ride it truly worthwhile. The Seaside's ziplines are more than four times the length of those on Royal Caribbean International's Oasis-class ships, the first to feature a zipline.
A ride starts with a liability waiver that must be signed before the rider climbs a steel stair tower just to the rear of the funnel. There are platforms along the way where riders of the Seaside's two largest waterslides get ready to launch.
On a midafternoon visit during my preview cruise in late December, the wait to get to the top of the tower was a manageable 15 minutes. But I can see this being a very popular attraction at peak times on a full cruise.
A rider prepares to launch on the longest zipline at sea, onboard the MSC Seaside. Photo Credit: TW photo by Tom Stieghorst
Arriving at the jumping-off platform, riders see what look like the large cargo bins in the bellies of passenger jets. These are full of safety gear: helmets, harnesses and pulleys used to attach riders safely to the line.
As you get strapped in, it's natural to get a little anxious about the upcoming experience. Some 20 decks above the ocean, the vista at the top of the funnel is impressive, and the drop looks daunting.
Once harnessed, there is a small blue platform that elevates riders about 2.5 feet so they can actually be attached to the line.
A safety assistant communicates with a colleague at the other end to make sure the line is ready and clear, and then riders are released into the open air above the pool deck.
I always find that getting ready to ride and watching others do it makes me nervous, while actually riding the zipline is fun. MSC has threaded the zipline through a set of tubular metal rings about 10 to 12 feet in diameter. Riders sail through the rings, then pass over sunbathers and a raised helipad to another set of rings where the brakes are applied and the ride ends. The whole thing takes about 20 seconds.
One caution for riders is to come dressed in clothes, rather than swimsuits, and wearing closed-toe shoes. Those are requirements, and it isn't much fun to get to the head of the line only to be sent back to your cabin to change.