Cruise Secrets: How Ships (Mostly) Keep You From Getting Seasick

Fear of getting seasick on a cruise is the number one reason cited by people who say they’re afraid to go on a cruise, according to a statistic I made up. Seriously, lots of people I talk to about my cruises are intrigued by my tales of exotic lands, bountiful buffets, and countless cocktails bars. But they’re reluctant to experience a cruise for themselves because they fear spending a week on a rocking boat will turn into a days-long barf fest — which would be great to avoid the typical cruise vacation weight gain but not exactly conducive to a fun trip.

“But most of the time, you can hardly feel the ship moving,” I respond to the reluctant cruiser.

“Really,” the reluctant cruiser usually responds, “and how do they do that?”

“….?”

Tired of drawing a blank or changing the subject (“The buffets really are amazing) whenever I was asked that question, I resolved that the next time I stepped on a cruise ship, I would find out why it is that, except for extremely rough seas (something I’ve experienced only once in 10 years of cruising), you can barely feel movements aboard modern cruise ships.

Related: How to Avoid Getting Seasick on a Cruise (and What to Do If You Do)

Cruise ships don’t always have the benefit of such steady seas. So how do they retain relatively smooth sailing in rough waters? (Photo: Princess)

During a recent Alaska cruise aboard the Princess Cruise Line’s Star Princess, I got my answer.

“We use stabilizers,” the ship’s captain, Stefano Ravera, told me during a tour of the bridge when I asked how cruise ships remain steady. I’d heard the term “stabilizers” before, but to me it was always abstract technobabble — kind of like the “inertial dampeners” they were always talking about aboard the Enterprise on “Star Trek: The Next Generation.” I had no idea what stabilizers were or how they worked; they just sounded like something cool a ship’s captain would order to a crewman: “Extend the stabilizers!” “Aye-aye, sir!”

Related: 12 Things You Need to Know About Taking a Cruise in Alaska

Turns out, stabilizers are not technical mumbo-jumbo; they are real and are relatively simple. As Captain Ravera explained to me, a ship’s stabilizers are basically fins, about 7.5 meters (25 feet)-long that extend out from either side of the ship. They typically reside below the waterline, which is probably why you’ve likely never seen them unless the ship’s in dry dock.

The Star Princess, like the ship in this graphic, has two fin stabilizers, one on each side. (Photo: Wikimedia Commons)

“We have two: one on each side [of the ship],” Captain Ravera explained to me aboard the Star Princess. “Larger vessels, like aircraft carriers, have four,” mostly because one can’t be rolling back and forth when you’re launching planes and firing missiles.

On a cruise ship like the Star Princess, I guess we have to get away with only two stabilizers, as we aren’t tasked with delicate jobs like firing artillery. But a steady ship is still very much appreciated if you’re trying to dance “The Macarena” after a few Mai Tais in the dance club at 2 a.m. (or so I’ve heard). So how do stabilizer fins accomplish that task?

“They smooth the roll of the ship,” Captain Ravera said. “Roll” refers to the side-to-side movement you experience on a vessel at sea. The stabilizers adjust and tilt to counterbalance that rolling effect. “When the ship rolls to one side, the ‘down’ fin lifts and the upper fin goes down,” he says. “They’re cutting through the water and creating a drag and dampening the ship’s movement.”

Here’s what a ship’s stabilizer looks like. (Photo: Hannes Grobe, Alfred Wegener Institute/Wikimedia Commons)

But like all technology, stabilizers have their limits. They’re great for reducing the side-to-side movement on a vessel, a.k.a. the roll. But as seafarers know, there’s still the matter of the pitch.

“The pitching of the vessel — which is the up and the down, fore and aft movement of the vessel — cannot be dampened by any type of instrument or equipment,” Captain Ravera told me. He says the only way to adjust for that is changing the ship’s course, so that they’re hitting the waves at a different angle that hopefully will reduce the up and down movement.

So there it is: a crash course in how ships stay steady (or mostly steady) at sea, thanks to our friends, the stabilizers. Do they always prevent seasickness? No. (Click here for tips on accomplishing that task.) But thanks to stabilizing technology, cruise ships are much, much steadier than they were in days of yore. So if you’re on a cruise ship and you do feel significant rocking, rest assured that either the seas are amazingly choppy, or maybe you should take it easy on the Mai Tais.

WATCH: Did Sinbad Get This Seasick? Hitting the High Seas of Oman

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