Displacement, in the context of marine terminology, refers to the mass or volume of water that a ship's hull displaces when it is submerged. This quantity is often measured in tons and represents the buoyancy of the ship or its weight carrying capacity. It can also be visualized as the amount of water that would be required to fill the underwater volume of the ship's hull to the waterline level. In the case of a displacement hull, it refers to a specific type of ship or boat design where the hull is shaped in such a manner that it displaces water smoothly and evenly as it moves through it, rather than having a tendency to rise and plane or skid across the surface of the water. The displacement hull capitalizes on buoyancy and stability to push water aside, maintaining contact with the water surface, ensuring a smoother, more stable ride, especially in rough waters.

1. Ocean Liner: An ocean liner's hull is a prime example of displacement. As the massive structure moves through the ocean, it displaces a large amount of water equivalent to its own weight. This displacement allows the ship to float and navigate across seas. 2. Submarines: Submarines, when submerged, displace an amount of water equal to their own weight, allowing them to maintain a state of equilibrium under water. They adjust their displacement to ascend, descend or maintain a certain depth. 3. Canoe: Less massive than an ocean liner or submarine, a canoe still provides a good example of displacement. It is designed in a way that displaces sufficient water for it to stay afloat even while carrying loads like people or goods. 4. Icebergs: When an iceberg breaks off from a glacier and falls into the ocean, it displaces a huge volume of sea water. The weight of the displaced water equals the weight of the iceberg, hence it stays afloat. 5. Oil tankers: These are specially designed with a hull that significantly displaces water, allowing it to carry hundreds of thousands of tons of oil. It is this displacement of water that keeps the heavily loaded tanker buoyant.

Fun Fact: The concept of displacement in a nautical context is directly related to a principle discovered by the Ancient Greek mathematician, Archimedes. In fact, it's known as Archimedes' Principle. According to this principle, the weight of water displaced by a hull is precisely equal to the buoyant force that is exerting an upward thrust on the hull. This means that a ship will float when it has displaced its own weight in water. This is why large, heavy ships made from steel can float - despite steel being denser than water. Essentially, the air inside the hull of the ship keeps it afloat, displacing a volume of water that weighs the same as the ship itself. Moreover, a 'displacement' hull is designed to smoothly push water aside as it moves, instead of cutting through the water or riding on top of the waves. This allows for a smoother, more comfortable ride at slower speeds. However, these types of hulls are typically limited to a particular maximum speed known as the 'hull speed', due to increased resistance as they try to displace more and more water. Nevertheless, they are energy efficient at lower speeds and commonly found in trawlers, sailboats, and submarines.