Combine all salsa ingredients in a bowl and gently toss. Refrigerate salsa until fish tacos are ready to serve.
Evenly cut fish fillets into 8 strips. Place flour in one shallow bowl, place panko bread crumbs with salt and pepper in a second shallow bowl and whipped eggs in third shallow bowl. Dredge fish strips in flour (shaking off excess flour), then dredge in egg, then coat with bread mixture and gently place on a platter.
Heat coconut oil in a large skillet over medium-high heat. When oil is hot but not smoking, gently place 4 fish strips in skillet and cook until golden brown and crispy, turning only once. Transfer cooked fish to a plate lined with paper towels. Cook second batch with same technique.
Serve fish in warm tortillas and top with watermelon salsa.