The main message of this poem is a mand trying to make difference to the starfish by chucking them back into the ocean. And another man says that what he is doing is useless.
"I guess I should have asked, why are you throwing starfish in the ocean?" "The sun is up and the tide is going out. And if I don't throw them in they'll die." "But, young man, don't you realize that there are miles and miles of beach and starfish all along with it. You can't possibly make a difference!"