Bring water to a boil in a large skillet. Add salmon; reduce heat, and simmer 7 minutes or until fish flakes easily when tested with a fork. Remove from skillet; place in a shallow dish. Cover and chill.
Combine the tomato and next 8 ingredients (tomato through salt). Cover tomato mixture and chill 30 minutes.
Place 1 toast slice on each of 4 plates; top each with 1 cup tomato mixture and one fillet. Garnish with basil sprigs, if desired.