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.

The "fin" structures associated with cruise ships in 2026 usually refer to stabilizer fins, though these are actually located on the sides of the hull underwater, rather than exclusively at the back. These fins act like short airplane wings and extend from the ship's sides to reduce rolling (side-to-side motion) by up to 90%, ensuring a smoother ride for passengers. However, if you are referring to a vertical structure on the very top-rear of the ship, that is usually the funnel (the exhaust stack), which modern ships like those from Virgin Voyages or Celebrity have designed to look like a sleek, aerodynamic fin. Another "fin-like" component at the very back (stern) below the waterline is part of the Azipod propulsion system. Unlike traditional rudders, these pods can rotate 360 degrees, allowing massive 200,000-ton ships to maneuver into tight ports with incredible precision without the need for tugboats. These pods often have small fins or "nozzles" to help direct the thrust efficiently through the water.