The ocean that closes around Nandīśvara, 3,27,68,00,000 yojana wide. Ordinary water.
Twice the width of the continent it surrounds, as every ocean is. After the four flavoured seas the water goes back to being water and stays that way for the rest of the universe.
Past it the rings continue - Aruṇa, Aruṇavara, Aruṇābhāsa, Kuṇḍala, Rucaka and onward - innumerable, doubling forever, until Svayambhūramaṇa closes the middle world.
The middle world, ring by ring - Nandīśvaroda highlighted