The pet carrier is made of Mesh material which is water resistant. However, the removable pad inside is made of cotton and that is not water resistant.
Yes, there's still great airflow from the top.
Yes, you can load from the top, the front or the sides!
It has a hard dense 1/8 inch base that doesn't bend with 1/4 inch foam padding on top - both are in a zippered fitted cover of which the bottom is thick nylon - looks water/rip resistant and top is soft fuzzy material.