The Supreme Lord, Vishnu is said to recline on an ocean of milk. This is mentioned in Bhagavatam 8.5.24:
ity ābhāṣya surān vedhāḥ
saha devair arindama |
ajitasya padaṁ sākṣāj
agāma tamasaḥ param ||
Śrī Śuka said: O Mahārāja Parīkṣit, subduer of all enemies, after Lord Brahmā finished speaking to the demigods, he took them with him to the abode of the Supreme Personality of Godhead, which is beyond this material world. The Lord's abode is on an island called Śvetadvīpa, which is situated in the ocean of milk.
In the Bhagavatam, the churning of the milk ocean by the Devas and the Daityas is also described in great detail. Here is one of these verses:
unmathnatām amṛta-labdhaya ādi-devaḥ |
pṛṣṭhena kacchapa-vapur vidadhāra gotraṁ
nidrākṣaṇo 'dri-parivarta-kaṣāṇa-kaṇḍūḥ ||
The primeval Lord then assumed the tortoise incarnation in order to serve as a resting place [pivot] for the Mandara Mountain, which was acting as a churning rod. The demigods and demons were churning the ocean of milk with the Mandara Mountain in order to extract nectar. The mountain moved back and forth, scratching the back of Lord Tortoise, who, while partially sleeping, was experiencing an itching sensation.
It is written in the Bhagavatam 5.20.18 that the Dvipa (island) known as Kushadvipa, which is a part of the Bhumandala (the Earth) is surrounded by an ocean of milk:
tathā ghṛtodād bahiḥ krauñcadvīpo dvi-guṇaḥ sva-mānena
kṣīrodena parita upakḷpto vṛto yathā kuśadvīpo ghṛtodena
yasmin krauñco nāma parvata-rājo dvīpa-nāma-nirvartaka āste
Outside the ocean of clarified butter is another island, known as Krauñcadvīpa, which has a width of 1,600,000 yojanas [12,800,000 miles], twice the width of the ocean of clarified butter. As Kuśadvīpa is surrounded by an ocean of clarified butter, Krauñcadvīpa is surrounded by an ocean of milk as broad as the island itself. On Krauñcadvīpa there is a great mountain known as Krauñca, from which the island takes its name.
Now my question is that are all these three oceans of milk (the one on which Vishnu lies, the one that was churned by the Devas and Daityas, the one that surrounds Kusadvipa) the same ocean?