Personalized 1st Birthday Submarine Youth T-Shirt. Cute 1st Birthday Submarine Youth T-Shirt - Black has number 1 on the porthole for your child's undersea party. Let the good times roll in a durable T-Shirt that takes kids from school to play in an amazing array of colors. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar.