Tabbouleh with Tuna

2 cups water

6 scallion s, white bulbs only, sliced thin

1 cucumber , peeled, halved lengthwise, seeded, and cut into 1/4-inch dice

6 radish es, sliced thin

1 carrot , grated

1/4 cup chopped fresh parsley

1/4 cup chopped fresh mint

1 6-ounce can tuna packed in oil

2 tablespoons olive oil

1/3 cup lemon juice (from 2 lemons)

3/4 teaspoon salt

1/4 teaspoon fresh-ground black pepper