How Does a ‘Cruise Ship’ Stay Afloat With So Many People Onboard?

A cruise ship stays afloat because it is designed like a giant boat, and boats stay on water by using buoyancy. Buoyancy is when something pushes up against the water, keeping things from sinking, just like how a balloon floats in air! Imagine you are floating in a bathtub with a lot of toys around you, even though there's a lot going on, you still float because your body and the toys displace water. That’s what happens on a cruise ship: it displaces so much water that it can hold many people without sinking.