Sri Ram could not think of any possibility to reach Lanka with his 10 million Vanaras (monkeys) army that he takes out his arrow to dry the ocean. Then the ocean god appears and asks for forgiveness and not to dry him rather take help from Vanara architects Neel and Nala to construct a bridge over it to Lanka.
With the instruction of Neel and Nala, Vanaras threw stone with the name of Lord Rama himself inscribed on it. Every stone floated on the water with the name and it took 5 days to complete the gigantic bridge later known to be Rama Setu. This has a spiritual significance. When the name of the Lord is with you, you will float through the ocean of misery; you won’t sink in the world of misery.
While all the Vanaras threw stones carved with the name of Sri Rama, all floated. Seeing this Rama himself tried to throw the stone, but it sank. He was surprised and could not figure out that when Vanaras did the same thing would work and when he tried wouldn’t. One of the Vanaras was watching this act of Rama and started laughing. Rama feels embarrassed and realizes that it is the power of the devotee towards him that helped the stone to float. The moral of the story is that the devotees of him are more powerful than himself.