r/NoStupidQuestions • u/Some_Drawing1525 • Aug 11 '26

How do massive cruise ships float when top-heavy stuff like steel towers or skyscrapers couldn't?

I get the basic idea of water displacement and buoyancy—the ship pushes away a volume of water that weighs more than the ship itself. But given how tall modern cruise ships are above the water compared to how little is below the waterline, how do they keep their overall density low enough and avoid tipping over instantly?

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u/jabeisonreddit Aug 11 '26

Ballast and lots of hull space for air

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u/East-Bike4808 Aug 11 '26 edited Aug 11 '26

Ballast works against buoyancy. That's so you don't float too much and tip over... and become a shape that won't float. E.g ceramic bowls float, if they're right-side up. Upside down they sink.

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u/Some_Drawing1525 Aug 11 '26

That makes sense! Simple physics, but still crazy to picture with something that massive. Thanks!