The legend that follows is one of the oldest of Vietnam, reputedly going back to the early years of the semi-legendary Hong Bang dynasty. It is probably of Taoist inspiration and affirms a belief in genie and immortals.
The third King Hung Vuong had a beautiful daughter named Tien-Dung (Divine Beauty), who, although of fairy-like loveliness, was endowed with a whimsical nature. Despite her father's entreaties, she rejected every offer of marriage, preferring, as she said, to remain single in order to satisfy her passion for visiting the many beautiful sites of her father's kingdom, known as Van Lang. As the king loved his daughter tenderly, he tried to please her in every way possible, even placing at her disposal a number of vessels including the royal barge, so that she could navigate the rivers of the realm.
At that time, in the village of Chu Xa (Hung Yen province), lived Chu Cu-Van and his son Chu Dong-Tu (Marsh Boy). They were poor fishermen whose home had been ruined by fire. They had lost all their clothing except a single loincloth, which they took turns wearing. When Chu Cu-Van fell seriously ill and felt death approaching, he called his son to the side of his mat.
"After my death," he said, "keep this loincloth for thyself."
But Chu Dong-Tu was a pious son and could not let his old father be buried without shroud. He attended the funeral in borrowed clothes and then found himself without a garment of any kind. The poor young fisherman was obliged to do his fishing at night. During the day he would attempt to sell his catch to the people in the boats passing along the river, remaining immersed in the water up to his waist. One day, Princess Tien Dung, then in her twentieth year, accompanied by a brilliant suite, happened to approach the very place where Chu Dong-Tu was standing in the water. When the young fisherman heard the sound of gongs and bells and perceived the wonderful array of parasols and banners, he became frightened and took cover behind some bulrushes. Then he quickly dug a hole in the sand and covered himself so completely that only his nose was exposed.
Taking a liking to the picturesque surroundings, the princess expressed a desire to bathe there. A tent was set up on the shore. The princess entered, disrobed, and began to pour water over her head and shoulders. As the water trickled to the ground, it washed away some of the sand, exposing Chu Dong-Tu in all his nakedness.
"Who are you?" asked the princess. "What are you doing here?"
"Your Royal Highness," replied the frightened youth, not daring to raise his eyes, "I am only a poor fisherman. Having no garment with which to clothe myself, I was forced to hide in the sand at the approach of the royal barge. Will you not pardon my error?"
Princess Tien Dung dressed in haste and threw a remnant of cloth to the young man so that he could cover himself. Then she questioned him in great detail about his past life. Hardship had not marred Chu Dong-Tu's handsome features, and the princess was not displeased with his demeanor. After some deliberation, she reached a decision.
"I had not expected to marry," she said with a sigh, "but Heaven has ordained this meeting. I cannot oppose Heaven's Will."
She immediately ordered all her officers and ladies to come forward. When they had assembled, she told them of the extraordinary adventure that had just befallen her. Then she announced that it was her intention to marry the young man.
"But Your Royal Highness," cried Chu Dong-Tu on hearing these words, "how can I, a penniless fisherman, be the husband of a royal princess?"
"It has been predestined," replied the young woman; "therefore, there can be no reservations about the matter."
"Long live Their Royal Highnesses." cried the officers and ladies in chorus.
Chu Dong-Tu was properly clothed and groomed and the royal wedding took place that same evening with great pomp. But when King Hung-Vuong learned of it, he became furious and shouted angrily at his courtiers.
"In marrying a vagabond," he said, "Tien Dung has dishonored her rank of royal princess. She is to be disinherited and forever banned from my court." The princess had no desire to face her father's wrath. In order to provide for her husband and herself, she decided to go into business. She sold her junks and her jewels, bought some land at a crossroads near the village of Chu Xa, and established a trading post. Visited by merchant vessels from the entire kingdom of Van Lang and from countries overseas as well, the village prospered and in time became a great emporium.
One day, a foreign merchant advised the princess to send an agent across the sea to purchase some rare merchandise that could then be sold at a tenfold profit. Chu Dong-Tu was charged with this mission and together with the foreign merchant left by sea. On reaching the island of Quynh Vien, they met a Taoist priest who immediately recognized the sign of immortality on Chu Dong-Tu's forehead. The former fisherman then entrusted his gold to the foreign merchant and remained on the island for one year in order to be initiated into the secrets of the Way (Dao).
On the day of Chu Dong-Tu's departure, the priest gave his disciple a pilgrim's staff and a conical hat made of palm leaves. He advised him never to be without them.
"This staff will give you support," he said, "but it is worth much more. The hat will protect you from the rain and also from harm. Both have supernatural power."
On returning to Chu Xa, Chu Dong-Tu converted his wife to Taoism. They repented their earthly sins, abandoned their possessions, and left in search of a deserted place, where they would be able to devote themselves entirely to a study of the True Doctrine.
All day they stumbled on through the wilds and at last fell to the earth exhausted. But before lying down to sleep, Chu Dong-Tu planted his staff in the ground and on it hung the conical hat.
The couple had been asleep only a few moments before being awakened by a crash of thunder. They sat up between flashes of lightning and saw a magic citadel suddenly rise from the earth. It was complete with jade-and-emerald palaces, public buildings, and houses for the inhabitants. Mandarins, both civil and military, courtiers, soldiers, and servants came forward to welcome them to the city, begging them to rule over the new kingdom. Chu Dong-Tu and his wife entered their palace and began a reign of peace and prosperity.
When King Hung-Vuong learned of the existence of the magic citadel, he thought that his daughter had rebelled against his authority and was desirous of founding a new dynasty. He assembled an army and ordered his generals to destroy the rival kingdom. The people of the citadel urged the princess to give them weapons so that they might defend her territory.
"No," she said, "I do not intend to defend this citadel by force of arms. Heaven created it and Heaven has sent my father's army against it. In any case, how can a daughter oppose her father's will? I must submit to the inevitable."
That evening King Hung-Vuong's army camped on the bank of the river opposite the magic citadel. His generals planned to attack the following morning. But at midnight a terrible storm arose and the entire citadel with all its inhabitants was seen to rise into the air and disappear. The next morning the royal army found only a marshy pond and a sandy beach at its former sight. The pond received the name of Dam Nhat Da, which means "Pond Formed in One Night", the beach was called "Spontaneous Beach", or Bai Tu-Nhien.