Bring a pot of salted water to boil and add the noodles. Cook as indicated then drain and rince under cold water. Set aside to allow to drain completely
Combine Lime juice, 3 tablespoons of water, sugar, chilie sauce and fish sauce
Add the cucumber, onion, watermelon and noodles. toss to combine.
Season with Salt and Pepper. Set aside to marinate
Season the steak with salt and pepper. Grill until marked (about 3 minutes per side)
Move to a cutting board and allow to rest for about 5 minutes
Cut into strips against the grain
Serve the steak over the bed of the noodle mixture topped with some fresh chopped cilantro