Apam Napat is a deity mentioned in the Rig Veda. In Vedic text Apam Napat dwell in waters, emanating brilliance and is surrounded by water in the form of young maidens who purify him. He should be propitiated before drawing water. He is sometimes equated with Hindu God Agni.
He is golden in form and appearance and is always shining.
He travels on steeds. His movement is compared to the swiftness of thoughts. His food is ghee.
Rig Veda X, 30, 3-4 Verse dedicated to Apam Napat –
Adhvaryus, go to the waters, to the ocean! Sacrifice to Apam Napat with the offering! My he give you today the well purified water…
Thou shinest without fuel amidst the waters, thou whom the priests revere in sacrifices, Apam Napat, give the sweet waters by which Indra is strengthened for heroism.
Apam Napat, then, is the essence and the custodian of the force that the essence represents. The brilliance with which he glows, a pure divine radiation, illumines those that honor him.
Due to his self shining nature without any fuel source, he is equated with Agni.
Agni in some hymns in Rig Veda is equated with Apam Napat.
Source – Myth in Indo-European Antiquity By Gerald James Larson, C. Scott Littleton, Jaan Puhvel
Source – Vedic Mythology By Arthur Anthony Macdonell