Pat tenders dry and season with salt and pepper. Put flour in one shallow dish, beat egg with egg-wash water in another and mix cornmeal and Parmesan in a third. Coat each tender lightly with flour, dip in egg and press into the cornmeal mixture; discard unused coating mixtures.
Heat 2 tablespoons oil in a 12-inch skillet over medium heat. Cook 6 tenders for 3 to 4 minutes per side until golden and 165°F inside, then transfer to a clean plate. Repeat with 2 more tablespoons oil and the remaining 6 tenders.
Carefully wipe loose dark crumbs and excess oil from the empty skillet with paper towels held in tongs. Lower heat to medium-low, add remaining tablespoon oil and cook garlic for 30 seconds.
Add crushed tomatoes, oregano and sauce water. Simmer for 8 to 10 minutes, stirring occasionally, until the sauce thickens enough to coat a spoon.
Arrange cooked tenders over the sauce with some edges exposed, overlapping slightly if needed. Spoon a little sauce across their centers, scatter mozzarella over them and cover over low heat for 2 to 3 minutes until the cheese melts.
Remove from the heat and serve 3 tenders with tomato sauce per portion.