Combine curry paste and water in a small bowl; stir well with a whisk.
Coat a Dutch oven with cooking spray; place over medium heat until hot. Add curry paste mixture and shrimp; cook, uncovered, 4 minutes, stirring frequently. Add onions, peas, and bell pepper; cook 3 minutes or until peas are tender.
Add coconut milk and cilantro; cook 2 minutes or until thoroughly heated. Stir in salt. Remove from heat, cover, and let stand 5 minutes before serving.