Combine the water, red lentils, and 1/4 teaspoon salt in a medium saucepan. Bring to a boil; cover, reduce heat to medium-low, and simmer for 20 minutes. Drain and set aside.
Combine 1/4 teaspoon salt, mint, and the next 5 ingredients (mint through curry powder). Combine 1/4 cup mint dressing, torn spinach, mushrooms, and bell pepper; toss well to coat. Combine lentils and 1/4 cup mint dressing, and toss well to combine.
Arrange 2 cups spinach mixture on each of 4 plates; top each serving with 1/2 cup lentil mixture. Divide shrimp evenly among salads; drizzle with remaining dressing.