Combine tuna, mayonnaise, celery, and pickle relish in a mixing bowl. Stir well with a fork; set aside.
Place one French roll on a cutting board; carefully cut a thin slice, lengthwise, off the top of the roll. With your fingers hollow out the roll by removing some of the soft bread; leave about a 1/2-inch shell. This makes the "boat" for the sandwich. Prepare the other rolls the same way.
Line a paper plate with a paper towel. Place the "boats" on the plate. Sprinkle 2 tablespoons of shredded cheese into each "boat". Fill the "boats" with tuna mixture. Sprinkle with remaining shredded cheese.
Place a paper towel over the sandwiches; microwave on HIGH for 2 to 2 1/2 minutes, until cheese is melted. Cut the slice of American cheese diagonally. Thread a toothpick to make a sail. Place a sail in each boat. Top with sliced olives.
