Boil the Pasta: In a large pot, bring salted water to a roaring boil. Add the fettuccine or linguine and cook according to the package instructions until al dente. Drain the pasta, but reserve 1/2 cup of the starchy pasta water.
Combine Everything: Add the cooked pasta to the skillet, tossing to coat every strand. Gradually add reserved pasta water until desired consistency. Fold in the shrimp and scallops, and garnish with fresh parsley before serving.
Notes
For an extra kick, consider adding more red pepper flakes or splash of white wine to the sauce.