Ganesha tells us of Vishnu's first incarnation...
After each of Vishnu's incarnations, he would come to visit me and tell me the story of his new adventure. Vishnu always wanted to tell me the story right away so that all of the details were still fresh in his mind. As a god he has excellent memory but, perhaps, his incarnations as human have made him believe he would have such a mortal flaw. Of course, I am always happy to oblige a request from Vishnu. No matter what I am doing at the time, I set aside my other writings, take out a new parchment, grab some more ink, and prepare myself to write down whatever the god wishes to tell me.
This particular story of Matsya was one of my favorites. Vishnu told me that he had been listening to the prayers and devotions of a great man named Satyavrata, when the god Brahma approached him. Brahma had foreseen a disaster that would occur and wanted to warn Vishnu. He told Vishnu that it was his responsibility to pick out the most deserving person on the earth to warn of this disaster and ensure the people's survival through this time. Vishnu could think of no one more devoted to worshipping him and the other gods than the man he had just been listening to. Satyavrata. Brahma told Vishnu that he agreed with his pick and then turned Vishnu into a tiny fish and sent him down to earth to be found by Satyavrata. Here is what happened next...
Satyavrata, Saty for short, was down by the river for his morning prayers to the god Vishnu. His morning prayers were his daily ritual to lord Vishnu. After he picked himself up off the grass, Saty went over to the river to wash his hands and cleanse himself. While he was washing his hands a tiny green fish swam into the gap of his cupped hands. The fish was extremely small, no bigger than his pinkie, and he assumed it was just a baby. The fish appeared frightened, as the size difference between the two was enormous. Saty spoke the language of the animals and proceeded to try to comfort the small fish so that it did not die from shock. The fish was pleading for his life but Saty told him there was no need because he could never harm such an innocent creature. Once Saty began to talk, the fish immediately calmed down. Saty found out that the name of the little fish was Matsya and that he had been separated from his large family by getting caught in a strong current.
Saty felt bad for Matsya, and decided that he was going to take care of him. He cupped Matsya in his hand with plenty of water and walked his many miles home. He was extremely careful the whole trip and never let any of the water leave his hand. When he reached home, Saty showed his wife the small little fish and asked her to find something to keep him safe. His wife, Neha, brought him a small little cup, which was more than enough room for Matsya.Matsya knew that he would always be safe in Saty and Neha's protection and so he swam around in joy.
Matsya was not a normal fish, though, as they would soon find out. Within days, Matsya had grown to the size of Neha's small hand. She moved Matsya to a large bowl to make sure that he always had enough room to swim. A few days later and Matsya had already outgrown the bowl. Saty carried the fish to the small pond that was behind their home. This growing kept happening until Matsya had outgrown the pond, a stream, a lake, and a river. Saty was not going to give up on Matsya because he felt an unnatural devotion to the once small creature. He was extremely drawn to him and felt that he must protect him at any cost. Matsya, in return, was always grateful to the help of Saty.
The next move and presumably the last was Saty putting Matsya into the ocean. He was in doubt that this would even be big enough to hold him but Saty was out of options, so he got on his knees and prayed to Vishnu. This triggered something in Matsya. He revealed himself as Vishnu and he began to speak of a prophesy. He told Saty that he had one week to prepare for a flood that would cover the earth, destroying everything. He told Saty to prepare his family and gather supplies and all of the animals that he could find. He told Saty that he would be back at the end of those seven days before the flood was to begin.
Saty took every word Matsya said as truth and finally understood his devotion to the fish due to his devotion to Vishnu. Saty prepared as Vishnu had advised him and at the end of the seven days, Vishnu appeared to him and his family. He brought a large indestructible boat that was built by the gods. He told Saty to board his family and load the supplies onto the boat. As Saty was closing the door behind him the rain began to fall. They witnessed the world flood and everything being destroyed, just as Matsya had told them would happen.
Vishnu appeared in the flooded earth as Matsya once more with finally enough water to survive. Matsya told Saty that he had been chosen because he was the most kind and loving human Vishnu had ever seen. Saty had shown his devotion to not only a god but also to a small helpless creature. Vishnu said there was hope in the world if all men were to come from this exceptional example of a man.
Kurma
Source: Wikipedia. Link
Avatara 1-Matsyavatara (Lord Vishnu in Fish Form)
Web Source: Samasya