Personalized Submarine 6th Birthday T-Shirt. THINGS ARE LOOKING UP 6th birthday T-Shirt - White with big number 6, colorful submarine, little deep sea explorer in the porthole and bright fish with bubbles. Wardrobe essential for looking good, 24/7. 5.0 oz., pre-shrunk 100% cotton. Seamless 1x1 rib collar. Shoulder-to-shoulder taping. Double-needle stitched sleeves, bottom hem and front neck. Note: greys are a cotton/polyester blend.