Place a live starfish on a wet surface, it will quickly attach itself to it using its strong suction cups. Try removing it, it won't be easy. It can even break open mussels with these strong suctions. Starfish use seawater to steer the feet. A smooth spot on top of the starfish is for filtering water. Its anus is also on top, precisely in the middle. Its mouth is exactly opposite, on the underside of the body.