Preheat oven to a low, warm temperature.
Line a baking sheet with a brown paper bag. Place baking sheet in the preheating oven.
Place tilapia fillets on a plate or cutting board.
Sprinkle fillets with salt and pepper.
Pour flour on a dinner plate. Spread evenly.
Beat the eggs with water in a shallow bowl or pie plate.
Mix cashews and bread crumbs. Place on a third plate. Spread evenly.
In a large skillet, heat a 1-inch layer of oil over medium-high heat until a candy thermometer registers 375°F.
Place a fillet in the flour. Turn to coat evenly.
Remove fillet, shaking off excess flour, and dip into egg mixture. Turn to coat evenly.
Remove from egg bowl, allowing excess to run off, and place on the cashew/bread crumb plate. Turn and press to coat evenly.
Place coated fillet on a clean plate.
Repeat with remaining fillets.
Carefully add breaded fillets, one or two at a time, to the hot oil. Do not crowd.
Fry 3 to 5 minutes, until fillets are browned, turn and cook 2 to 4 minutes longer. Remove from oil.
Place fried fillets on paper-covered baking sheet in the oven to keep warm.
Repeat with remaining breaded fillets until all are cooked.