Seven Oceans

1. Accepting the Lord's invincible semen, passionate and fortunate Viraja at once became pregnant.
2. After a hundred celestial years of pregnancy, she gave birth to seven handsome sons from the Lord.
3. In this way the Lord's eternal beloved became the mother of seven sons. She was very happy with her seven sons.
4. One day, her heart filled with amorous desires, the saintly girl again enjoyed pastimes with Lord Hari in a secluded place in Vrndavana forest.
5. Then, frightened by his brothers, her youngest son came there and went to his mother's lap.
6. Seeing her son was afraid, she who was an ocean of kindness left Lord Hari and placed the boy on her lap. Then Krishna went to Radha's home.
7. When she had comforted the boy she noticed that her beloved was no longer there. Her heart filled with unsatisfied desires, she lamented greatly.
8. She angrily cursed her son: "You will become an ocean of salt-water. The living entities will never drink your water."
9. Then she cursed all the boys: "Those fools will go to the earth! Fools, go to beautiful Jambudvipa on the earth!
10. "They will not stay together in one place, but will stay each in his own place. They will stay happily around different islands.
11. "They may enjoy pastimes with the rivers on these islands."
    In this way, because of his mother's curse, the youngest boy became an ocean of salt-water.
12. The youngest then told the other boys about their mother's curse. Unhappy, all the boys went to their mother.
13. After hearing their mother's words, they offered obeisances to her feet. Then, their necks bowed with devotion, they all went to the surface of the earth.
14. O sage, they became seven oceans around the seven islands. From the youngest to the eldest, each ocean was twice as large as the preceding one.
15. They became 
1. oceans of salt-water, 
2. sugarcane juice, 
3. wine, 
4. clarified butter, 
5. yoghurt, 
6. milk and 
7. sweet water. Their liquid will be used to cultivate grains on the earth.
16. In this way they became seven oceans around the seven islands of the earth. Unhappy in separation from their mother and brothers, all the boys wept.
17. Tormented by separation from her sons, chaste Viraja wept again and again. She fainted out of grief she felt for her sons and husband.
18. Understanding that she was drowning in an ocean of grief, Radha's master, His lotus face smiling, came to her again.
19. When she saw Lord Hari she stopped weeping and lamenting. Gazing at her beloved, she became plunged in an ocean of bliss.
20. Overcome with passion, she placed Lord Hari on her lap and enjoyed pastimes with Him. In this way, even though she had abandoned her sons, Lord Hari became pleased with her.
21. His eyes and face filled with happiness, He gave her a benediction: "Beloved, I will always come to you.
22. Like Radha you will be dear to Me. By the power of My blessing you will always protect your sons. 

Source
http://018g.blogspot.com/2013/03/brahma-vaivarta-purana.html

The whole earth is divided into seven islands or dweepas. The name of these islands is

1. Jambu, 
2. Plaksha, 
3. Varuni
4. Shalmali, 
5. Kraunch, 
6. Shaaka and 
7. Pushkar. 

All these islands are surrounded by such oceans on all sides. The content of each of these oceans is 

1. Salt. 
2. Sugarcane juice, 
3. wine
4. ghee, 
5. milk, 
6. curds and 
7. honey respectively. 

Jambudweepa is also known as earth. It stretches from south of Himalaya to the north of ocean. The total area is about nine thousand yojans. It is further subdivided into

1. nine land segments, 
2. seven mountains, and 
3. seven sacred rivers near the seven places of pilgrimage and many other rivers. 

Similarly 

1. the 'Plaksha' island is surrounded by ocean of salt on all sides and spread up in the area of one thousand yojans. 
2. The area of Shalmali island is twice as that of Plaksha island. It is surrounded by the ocean of honey. 
3. The are of Kusha island is twice as that of Shalmali island and is surrounded by the ocean of ghee. 
4. Similarly the Krauncha is surrounded by the ocean of curd and its area is thrice as that of Kusha island. 
5. The area of Shaka island is twice as that of Kraucha island and is surrounded by the ocean of milk. 
6. The ocean of sweet water surrounds the Pushkar island. Its total length is five thousand yojans and five lakh yojans respectively. 

The mountain Manas is situated in this island. The residents of these islands never attain old age. Lord Brahma resides in Mahaveet section of this island. The people living in this island get food without making any effort. 

Where are the seven oceans

The earth is balanced on the hood of Sheshnag. Lord Vishnu is the nurturer of this world. There are seven more worlds beneath the earth, which are

1. Atala(Earth), 
2. Vitala, 
3. Sutala, 
4. Rasatala, 
5. Tala, 
6. Talatala and 
7. Patal. Each of these worlds is ten thousand yojans in length and twenty thousand yojans deep. 

All these worlds are full of invaluable and priceless diamonds. The residents of each of these worlds enjoy all the luxuries and pleasures of life. The demons and the Nagas reside in these worlds. Source

Uma Samhita of Siva Purana