Starfish or sea stars as they are also known are NOT fish but members of the Phylum Echinodermata.
Special features of starfish or sea stars include :
members of the Class Asteroidea
have radial symmetry
five or more arms radiating out from a central body
have spiky skin
move on tube feet
can regenerate lost arms
can push their stomach out through their mouth to feed
Starfish or sea stars as they are also known are found in temperate and tropical seas all over the world - mostly in shallow water on coral reefs, in estuaries, on rocky bottoms and in rock pools below low tide. All are marine.