Diving with sea Turtles

I am a turtle with a hard shell on my back. Nothing can hit me, so to speak, invulnerable. My head is not only round, but smooth. My eyes flicker flicker, really like a beautiful girl. My nose is like two little holes. The mouth opens and closes like a little flower. Thick neck, a little short. What's special is that I can retract my head and limbs, whereas people can't. This is me, a bulletproof turtle.