Srimad-Bhagavatam: Canto 5 - Chapter 1 - Verse 32

Sanskrit:

जम्बूप्लक्षशाल्मलिकुशक्रौञ्चशाकपुष्करसंज्ञास्तेषां परिमाणं पूर्वस्मात्पूर्वस्मादुत्तर उत्तरो यथासंख्यं द्विगुणमानेन बहि: समन्तत उपक्‍ल‍ृप्ता: ॥ ३२ ॥

ITRANS:

jambū-plakṣa-śālmali-kuśa-krauñca-śāka-puṣkara-saṁjñās teṣāṁ parimāṇaṁ pūrvasmāt pūrvasmād uttara uttaro yathā-saṅkhyaṁ dvi-guṇa-mānena bahiḥ samantata upakḷptāḥ.

Translation:

The names of the islands are Jambū, Plakṣa, Śālmali, Kuśa, Krauñca, Śāka and Puṣkara. Each island is twice as large as the one preceding it, and each is surrounded by a liquid substance, beyond which is the next island.

Purport:

The ocean in each planetary system has a different type of liquid. How they are situated is explained in the next verse.