SB 5.1.32

jambū-plakṣa-śālmali-kuśa-krauñca-śāka-puṣkara-saṁjñās teṣāṁ parimāṇaṁ pūrvasmāt pūrvasmād uttara uttaro yathā-saṅkhyaṁ dvi-guṇa-mānena bahiḥ samantata upakḷptāḥ.
Synonyms: 
jambū — Jambū; plakṣa — Plakṣa; śālmali — Śālmali; kuśa — Kuśa; krauñca — Krauñca; śāka — Śāka; puṣkara — Puṣkara; saṁjñāḥ — known as; teṣām — of them; parimāṇam — measurement; pūrvasmāt pūrvasmāt — from the former; uttaraḥ uttaraḥ — the following; yathā — according to; saṅkhyam — number; dvi-guṇa — twice as much; mānena — with a measure; bahiḥ — outside; samantataḥ — all around; upakḷptāḥ — produced.
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.