Sadko lives in Novgorod-the-Great where he played his gusli (psaltery) to entertain people at feasts. Somehow it happened that he is not called to play for three days running. He grows bored, so goes to the shores of Lake Ilmen where he plays to himself. The lake becomes violent, slashing and roaring before the musician. Sadko gives up his playing and goes away. Then the same thing occurs a second and third time. In the latter case the Tsar of the Seas appears out of the water, thanks Sadko for his charming music and decides to reward him. He advises Sadko to wager his life against the Novgorod merchant's goods asserting that there are golden fish in Lake Ilmen. The musician does as the Tsar suggested at the next feast. But nobody believes him. Three merchants wager three stores of goods each, then all go to the lake's shore. Three times a net is cast and each time it comes up with a golden fish in it. Thus Sadko wins the wager, becomes a merchant, gains a lot of money through trading, builds a new house of white stone and invites people to a grand feast. At the feast the guests eat and drink their fill and boast to each other. One brags of his wealth, another of his distinguished blood. A clever man boasts about his old father, while an insane one brags about his young wife. Only Sadko sits silent, bragging of nothing. The guests urge their host on and eventually he boasts that he could buy all their goods. Thirty thousands golden rubles are at stake.
Next morning Sadko rises early, supplies his men lavish amounts of money and sends them to buy all the goods they can find in Novgorod. The following day he does the same and sees to his astonishment that twice as many goods have reached the town's market from Moscow. It makes him think: "If I buy Moscow goods then goods will start coming to the market from over seas. It looks as though I am not the richest man in Novgorod. The town of Novgorod is richer." He stops buying things, loses the bet and gives thirty thousand golden rubles to the winners.
The purchased goods are loaded onto thirty ships and the merchant sails to trade in faraway lands. There he sells all on board at a great profit, puts the gold and silver thus earned in casks and sail home.
A storm begins on the open sea. Waves beat the ships, winds tear their sales, and the ships stand still as if someone is holding them. "The Tsar of the Seas is demanding a toll be paid to him," Sadko realized and orders some casks of silver to be thrown into the water. That does not help though. Then some casks of gold are thrown overboard. But that does not help either. It becomes evident that the mighty ruler is demanding a human sacrifice. Sadko propose to cast lots. Each sailor writes his name on a piece of wood. Sadko writes his name on a piece of gold. The lots are put into the water. All the lots but Sadko's keep afloat. His lot sinks to the bottom. "There was something wrong with the lots," he says, "Make yours of gold, and mine will be of wood." But the result is the same: Sadko's lot goes straight to the bottom of the sea. It is clear who is wanted by the Sea.
Sadko makes his will and birds farewell to his comrades, who leave him floating on a plank of oak with his gusli then sail off once the sea is calm. Being very tired Sadko falls asleep and wakes up at the bottom of the sea. The Tsar welcomes his guest and asks him to play the gusli. He plays for one, two, even three days. The Tsar dances without taking the shortest of rests. Furious waves lash about in the seas, ships sink and people perish. Sadko rips the strings off his gusli. The Tsar stops dismayed. He wants Sadko to stay with him forever and offers three hundred sea beauties from which to choose one as a bride. None of them is to Sadko's taste. Another three hundred women parade in front of him, then three hundred more, then finally along comes Volkhova, whom he chooses. A great feast is held, after which Sadko goes to have a rest and wakes up on the shore of the Volkhova River, which connects Lake Ilmen with the seas. His ships are sailing along the river to Novgorod, and his comrades greet him with delight at seeing him alive. Sadko spends the rest of his life in Novgorod occasionally recalling his underwater adventures.

(Based on a Novgorod legend. English language retelling was done by Vadim Shchanitsyn)