"Mike" wrote...
In books about sailing, I have read that the keel, going through water,
produces lift in a similar way to a sail. Given that water is a
non-compressible medium, I wonder how this can be so. Has it ever been
documented?

Air flowing at subsonic speed is also treated as incompressible. Both are well
documented in all kinds of fluid mechanics and aerodynamics texts, experiments,
and studies.