Do carboxylic acids form hydrates like aldehydes and ketones?
Let me go against the previous answers, and say that they "do" form hydrates.
What you should consider is that the equilibrium towards such hydrates is extremely unfavorable, making them virtually non-existent.

There have been, anyway, clever ways of "blocking" those forms as orthoesters. If I recall correctly, Corey used a protecting group of the OBO family in the synthesis of a natural product.

A more recent paper, which describes a protecting group of that nature, is this:
https://pubs.acs.org/doi/abs/10.1021/ol047493n?journalCode=orlef7

Anyway, in normal mechanism-writing, that hydrate is not considered, being highly unfavored and unlikely to form.