Sea stars have arms called rays.  They can only live in salt water.  Many can be found along the tide line of the shore in Atlantic and Pacific coasts of the United States.  Others live at the bottom of the sea.  Adult sea stars can measure from 1/2 inch to 3 feet across.  It's common colors are gray, blue, purple, green, red, pink, orange, and yellow.  On the underside of a sea star there are two to four rows of hundreds of tiny tube feet, this is it's canal system.  Each tube has a sucking disk.  These suckers let the sea star to cling or climb to a steep surface.