Personalized Submarine 6th Birthday Youth Long Sleeve T-Shirt. THINGS ARE LOOKING UP 6th birthday Youth Long Sleeve T-Shirt - White with big number 6, colorful submarine, little deep sea explorer in the porthole and bright fish with bubbles. youth long sleeve t-shirt. Shoulder-to-shoulder taping. Youth: S(6/8), M(10/12), L(14/16), XL(18/20)