Add the water and a pinch of salt to a small saucepan. Bring to a boil. Add the elbow macaroni gradually and boil until tender, 8 to 10 minutes. Drain the macaroni in a colander and transfer it to a medium mixing bowl.
Add the tuna to the macaroni. Add the carrot and celery to the macaroni and tuna.
Add the mayonnaise, lemon juice, ½ teaspoon salt, an