One of the biggest concerns we hear from first-time cruisers is:

“What if I get seasick?”

It’s a reasonable question. You’re voluntarily climbing aboard a gigantic floating hotel and heading out into an ocean that occasionally has opinions of its own. I’m not one to be bothered by movements of the ship, nor is my wife. But I can empathize with those who suffer from motion sickness, and those who are worried it might happen to them.

The good news is that modern cruise ships are remarkably stable, and plenty of passengers go through an entire cruise without experiencing motion sickness. But if you know you’re sensitive to motion—or simply want to stack the odds in your favor—where you stay on the ship can make a difference.

Think Low and Midship

If seasickness is a concern, one of the safest bets is generally a cabin near the middle of the ship and on a lower deck.

There’s some actual physics behind this.

A ship can move in several different directions, but the movements you’ll notice most are pitching, where the bow and stern move up and down, and rolling, where the ship rocks from side to side.

The farther you are from the center of that movement, the more you’re going to feel it.

Think about a seesaw. The person sitting at the very end travels a lot farther up and down than something located near the center.

A cruise ship works somewhat the same way. Cabins toward the bow or stern can experience more movement from pitching, while cabins high above the waterline can travel through a larger arc when the ship rolls.

Get closer to the middle of the ship and closer to the waterline, and you’re generally closer to the ship’s centers of motion.

In other words:

Midship + lower deck = usually less movement.

The CDC specifically recommends avoiding areas of a ship where motion is greatest, such as the bow, while medical references including the Merck Manual recommend the middle of a ship close to water level for passengers susceptible to motion sickness.

Why Does Motion Make Us Sick Anyway?

Seasickness isn’t really your stomach deciding that it hates cruising.

The problem actually starts largely with your brain and inner ear.

Your inner ear contains the vestibular system, which helps your brain understand movement and balance. When you’re sitting inside a cruise cabin, your eyes may be looking at a perfectly stationary wall while your inner ear is saying:

“We are definitely moving.”

Your brain receives conflicting information, and for some people the result is dizziness, sweating, nausea and eventually the sudden realization that perhaps ordering the seafood buffet twice was a mistake.

This sensory mismatch is the most widely accepted explanation for motion sickness.

That’s also why looking at the horizon can help. Your eyes can finally see the movement that your inner ear is already detecting, which reduces some of that disagreement between the senses. Reading or staring at your phone can do exactly the opposite.

What Are the Chances You’ll Actually Get Seasick?

Unfortunately, there’s no meaningful percentage that applies to every cruise passenger.

Your chances depend on your own susceptibility, the weather, sea conditions, the ship, your itinerary and even how much exposure you’ve previously had to motion.

Some people can cross the Atlantic during rough weather while happily eating a cheeseburger.

Others start turning green when somebody mentions the word boat.

The CDC says that given strong enough motion, almost everyone with a normally functioning balance system can eventually develop motion sickness. Some people are simply much more susceptible than others. A history of motion sickness, migraine or certain vestibular problems can increase that susceptibility, and people often become more accustomed to a ship’s movement after spending some time aboard.

Should You Avoid a High Deck or Balcony Cabin?

Not necessarily.

If you aren’t particularly prone to motion sickness, I’d personally choose the cabin you actually want rather than obsessing over finding the mathematically perfect location aboard the ship.

We’ve stayed in cabins all over cruise ships, including plenty of higher-deck balcony cabins, without spending the week hanging onto the furniture.

But if you already know that boats, cars or amusement rides make you sick, that’s different.

In that situation, I’d seriously consider booking midship and relatively low rather than selecting a cabin near the very front of the ship on one of the highest passenger decks.

You can’t eliminate the movement of the ocean.

You can, however, avoid buying yourself a front-row seat to it.

And sometimes that’s all the advantage you need.