Water being mostly incompressible is not the same as having high compressive strength. Liquid water makes for a poor tooth or structural column.
Are you confusing "compressive strength" with compressibility?
Many materials would have compressive strength easily, just by being relatively uncompressible.
But most loads have a (troublesome) tensile component. Fundamentally, the ability of a rigid material to resist deformation (in the most general sense) is what is most important, and that requires tensile strength.
See this comment elsewhere in this sub-thread that explains it probably better than I did: https://news.ycombinator.com/item?id=43904800
> In mechanics, compressive strength (or compression strength) is the capacity of a material or structure to withstand loads tending to reduce size (compression). It is opposed to tensile strength which withstands loads tending to elongate, resisting tension (being pulled apart).
Google search AI summary states:
> Compressive strength is a material's capacity to resist forces that try to reduce its volume or cause deformation.
To be fair, compressive strength is a complex measure. Compressibility is only one aspect of it. See this Encyclopedia Britannica article [2] about how compressive strength is tested.
[1] https://en.wikipedia.org/wiki/Compressive_strength
[2] https://www.britannica.com/technology/compressive-strength-t...
These are well understood terms in the field. Unfortunately, this illustrates the bounds of ai in subfields like materials: it confuses people.
Water has very low compressive strength, so low that it freely deforms under its own weight. You can observe this by pouring some water onto a table. This behavior is distinct from materials with high compressive strength, such as wood or steel.
(I say "very low" instead of "zero" because surface tension could be considered a type of compressive strength at small scales, such as a single drop of water on a hydrophobic surface)
See this comment elsewhere in this sub-thread that explains it probably better than I did: https://news.ycombinator.com/item?id=43904800