0 as the freezing point of water isn't arbitrary though, and neither is boiling.

They're both very useful reference points since water is universally available and you can easily tell when it freezes and boils, it makes it comparatively trivial and accessible to create your own thermometer which is likely to at least generally agree with someone else's.

this is the one aspect where i kind of prefer imperial measurements for distance, basing measurements on the human body means everyone has easy access to a reference that is likely to be not too tremendously wrong.

Obviously not super relevant these days, but back in the day it was a pretty neat feature. Like fuck, it wasn't that long ago that the meter and the kilogram were still defined by a SINGLE specific object kept in a climate controlled vault.