No idea, what is the current “cooking” oil used in a varity of packaged cookies and crackers found at grocery stores, but samples from some un-salted “saltine” crackers, provide amazing results:
A cracker will float for 10 minutes without showing signs of absorbing the surrounding fluid.
The crackers are like waterproof cardboard with a smattering of “flavor.”
And they taste like cardboard.
To be fair, my homemade hardtack can do much the same. It takes breaking it up and putting it in boiling water to make it dissolve. That’s just flour, water and some salt. Of course, hardtack is ALSO flavored like cardboard.