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AnusStapler t1_j8wbs7n wrote

Because there is no way of measuring the total weight of a ship. And if it was there, it's not relevant. They measure the "weight" of a ship in displacement, so the amount (tons) of water is displaces. This is usually mentioned under "normal displacement" which means fully bunkered, staffed and 2 thirds of supplies.

It implies that a ship "weighs" less if you put it in a huge vat of alcohol, as well.

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GoGaslightYerself t1_j8wfu3y wrote

> It implies that a ship "weighs" less if you put it in a huge vat of alcohol, as well.

Yep, since alcohol is less dense than water, a ship floating in alcohol will sit deeper in alcohol than in water. Water density varies with salinity and temperature, too, so they have different Plimsoll or "load lines" painted on ships to estimate their weight in tropical fresh water (TF), freshwater (F), tropical saltwater (TF), summer temperate seawater (S), winter temperate seawater (W) or Winter North Atlantic (WNA)...a ship of a given weight will sit much higher in WNA water than TF water...

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Hanswurst107 t1_j8x2cd9 wrote

So what's the difference between "total weight" and displacement in freshwater?

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