Bring a large pot of water to a rolling boil and stir in salt. Add shrimp and cook for one minute, then remove shrimp with a slotted spoon.
Bring water back to a boil and add noodles. Cook for five minutes. Remove noodles and rinse under cold running water, and drain. Cut into managable size (approx. 8" sections).
Julienne carrots and cucumbers, remove ribs from lettuce and cut into fourths. Slice serranos, if using.
Set up a work area with noodles, shrimp, veggies, and herbs.
Rinse rice paper under running water on both sides, for a few seconds. You can also dip in a pot of cold water for a few seconds. Place wet rice paper on a cutting board, plate, or damp washcloth.
Add lettuce leaves, followed by carrots, and/or cucumbers to the bottom of the rice paper. Leave space on each sides to fold over the filling.
Top with a handful of noodles, shrimp, and a few mint or basil leave. Add serranos, if using.
Carefully pull the bottom of the wrapper up and over the filling until you're half way up the wrapper. Fold both sides in (similar to rolling a burrito). Continue rolling up until fully rolled. Repeat with the remaining ingredients.