How Does a Cruise Ship Stabilizer Work?

Wondering what a cruise ship stabilizer is and how it works? This article provides you with all of the information you need.

What is a cruise ship stabilizer? How does it work? Stabilizers serve an essential function on cruise ships. They are fins or rotors beneath the water line, extended from the ship’s hull to stabilize the ship and prevent it from rolling. This rolling could result from either wind or waves, and the stabilizer steadies the ship.

In general, you don’t need to worry about how the ship stays stable – that’s for the engineers to concern themselves with. However, if you’re curious, the following is a guide you can reference for your safety, comfort, and enjoyment.

How Do They Work?

Modern ship stabilizers – of which there are many types – are highly effective and efficient. Below, we describe the different types and how they function. 

Passive Systems

These systems don’t require external power or control. Examples include a bilge keel, fixed fin, and moving weight system.

Bilge Keels

These are used widely throughout the cruise ship industry. A bilge keel is an externally-fitted bulb plate that forces the water to move with the ship, which creates turbulence – a necessary controlled underwater force for smooth sailing – and reduces motion. It functions best at higher speeds. 

Active Systems

These systems use external power and control to provide a roll that opposes the natural roll of the water underneath the ship at any given time. Examples include active fins, gyroscopes, and active moving weight systems. 

Active Fins

Active fins use a roll sensor that conveys the roll angle and velocity to a main external controller. That controller processes these two factors using data algorithms and transmits back the correct response to counterbalance against the roll, using fins and hydraulic pressure. 

Cruise Ship Stabilizer Fin
Cruise Ship Stabilizer Fin (Photo Credit: Templar52)

Active fins have a relatively high 90% success rate, ensuring smooth sailing (literally). It also keeps the resale value of the ship high. Like bilge keels, active fins are less effective at very slow speeds, but there are modern technologies that can fix that. 

Active Anti-rolling Tanks

These work above the water line. These tanks use pumps or air pressure to control the water’s motion, decreasing roll while a second axial pump transfers water from one side of the ship to the other. The tanks time the water flow in sync with the ship’s roll, reducing overall roll and motion. 

While highly effective, there can be a lag time in filling the tanks, which would cause a delay in the tanks’ ability to stabilize roll effectively.

More on Stabilizers

Consider this section more casual parlance about stabilizers, in case the technical specs were too techy. People who board a cruise ship are sometimes afraid that the boat will rock so much as to make them seasick. We have great news to the contrary – that rarely happens!

The ship stabilizers are responsible for that stability. While a bit of motion here and there is inevitable, you likely won’t feel it unless there’s a disaster or an unexpected turn, which is rare. Check out the secret codes on cruise ships for more information about those phenomena.

For the active and passive finned stabilizers, a cruise ship’s stabilizers essentially act how you would expect fins to act in the water. They extend out from both sides of any given cruise vessel. They are usually below the waterline, invisible to passengers and crew, while engineers have access to them in case of an emergency onboard (i.e., they stop working).

Cruise Fin Stabilizer
Image Credit: Tosaka

Smaller ships have two, and larger ships and other vessels, such as military craft, have four. 

In layman’s terms, all “roll” means is the vessel’s movement at sea. Since you want to do all sorts of things that require stability, such as hitting the gym, dancing, or clinking wine glasses with friends – preventing roll is paramount. 

The fins adjust and calibrate according to the motion of the water. One fin lifts, and the other goes down. It’s all about balance. These motions help the ship stay stable and in equilibrium by cutting through the water and creating drag, no matter what the movement of the water will bring. Heavy storms are possible, but cruise ships are so elegantly and maturely designed that they know just what to do.

Technology has its limits, though. There is what’s called “pitch” on all maritime vessels. Pitch is the up-and-down movement of the ship, so lengthwise or horizontal motion. Manual labor is the way through that natural phenomenon – adjusting the ship’s course. With skilled captains at the helm, this won’t be a problem.


This is your go-to guide on ship stabilizers. We’ve provided both highly technical and highly accessible descriptions and specifications of stabilizers, including differentiating between the different types that are out there.

Read Also: Cruise Ship Propeller Size – How Big Are They?

We learned that finned stabilizers act like real water fins, balancing out the motion of the water and helping the ship compensate for it by creating drag. You might want to take this guide with you when you board a cruise ship for the first time or anytime. It will put you at ease.

Haiyan Ma
Haiyan Ma
I absolutely love cruising with my favorite ports of call being in the Caribbean. As a former crew member for Disney Cruise Line, Royal Caribbean, and Carnival Cruise Line I can continue my passion by sharing my experiences with readers. Find out more about us here.


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