Cruise ships can weigh more than 65 million kilograms. To be able to keep afloat and minimise swaying so that passengers have a comfortable ride, the cruise ship have to displace an equivalent amount of water which weighs the same as the ship. The hull, or body of the ship below the main deck, is typically very wide and has a deep base line, or bottom and it has a huge “U” shape. This is the concept of Upthrust / Archimedes Principle that is taught during our A Level Physics tuition lessons.
To ensure that the ship is as light as possible, the hull’s volume is mainly air, which has much lower density than water. The problem comes when the ship runs aground and water gets into the hull. And the “Titanic” story begins.