When a cruise ship is plying the open waters, it can look like an engineering wonder. With a deck plan that stretches from floor to ceiling, cafes, stores, swimming pools and casinos, the big ships leave unsuspecting passengers speechless.

While the amount of a cruise ship that is under water will vary depending on factors such as weight and the conditions of the sea, the average cruise ships only have around 10% of their total ship in the water at any given time. This is because the bulk of the cruise ship's weight is contained on a lower portion of the hull that keeps it low to the ground, preventing the vessel from tipping over in the seas.

The way a cruise ship stays afloat is through the use of buoyancy, which is the ability of an object to keep itself afloat. To achieve this, a ship must be made of lightweight materials that are denser than water.

A hull design that is wide, deep and rounded helps disperse the ship's weight across the body of the boat. This allows the hull to move in and out of the water with ease, which reduces drag, helps the vessel stay on track, and improves the ship's overall efficiency.

To keep a large ocean liner from tipping over in the water, a special type of stabilizer is used called hydraulic active fin stabilizers, which protrude out from the hull and can be activated quickly. These stabilizers also help the ship shift its center of buoyancy as it tilts from side to side, which prevents it from sinking and keeping it afloat on the surface of the water.