The boy in the story chucks the starfish back into the ocean to save their lives. It strikes me that in the course of the starfish's life, the contact with the boy is a relatively small moment. He only held each one long enough to toss it back into the water. That's a very short period of time, but it changed everything for the starfish.
In life, sometimes the smallest moments reach so far beyond anything we can ever see. There's no way for the boy in the story to know what became of the starfish he threw back. That wasn't his role in their lives. He was just there to toss them back in. It just shows me that nothing small we do for each other is ever too small. And it doesn't take a big effort sometimes to change everything for one person.