Whisk in the lime juice and the sweet chili sauce. You can add a little sugar if you want it sweeter. Set the sauce aside in the fridge.
Combine the chinese cabbage, carrot and the herbs with two tablespoons of the sauce. Fill a wide shallow bowl with hot to warm water.
Place one of the rice paper sheets into the bowl ensuring that it is covered with water. Let it sit for about 30 seconds or until softened, then transfer to a clean board.
Lay a piece of mint onto the rice paper about 4 centimetres from the edge closest to you and then lay three slices of the radish overlapping on top of each other onto the mint; lay across the rice paper three shrimp then top with a small amount of the salad.
Roll up the rice paper, fold the two sides of the rice paper over the filling and roll up with some of the watercress. Repeat with the remaining rice paper sheets. Serve with the sauce on the side.