Combine haricots verts, water, and carrots in a skillet over medium-high; bring to a boil. Reduce heat and simmer, partially covered, 6 minutes or until carrots are just tender. Increase heat to medium-high; cook, uncovered, 4 minutes or until liquid evaporates. Add butter; cook 2 minutes, stirring to coat. Stir in tarragon, salt, and pepper.