Oil -- typically olive oil -- symbolizes the good that comes from celestial love. Celestial love is love of the Lord, the highest and purest love we can have. The good of celestial love is the desire to be good springing from celestial love: Wanting to do the Lord's will because you love Him. That's not a state many reach, even in heaven, but it's a beautiful goal. This representation makes sense based on the idea that the sun -- the source of all natural light and heat, and thus all natural life -- represents the Lord, the source of all spiritual light, heat and life. Burning oil was the most pure fire available in Biblical times, thus the closest representation of the sun people could create.

'Waters' particularly signify the spiritual parts of a person, or the intellectual aspects of faith, and also their opposites.

'The waters above the firmament,' as in Genesis 1:7, signify the knowledges in the internal self, and 'the waters beneath the firmament' signify the knowledges of the external self.

'Waters,' as in Ezekiel 47:9, refer to the New Jerusalem, and they signify spiritual things from a celestial origin.

'Many waters,' as in Revelation 17:1, signify truths of the Word adulterated. 'Waters' or 'rivers' signify spiritual, rational, or scientific things pertaining to truth.

'Waters … that go softly,' as in Isaiah 8:6-7, signify spiritual things, and 'waters … strong and many,' signify falsities.

'Waters,' as in Psalms 104:3, signify divine truths.

'Waters' signify truths in the natural self, and in the opposite sense, falsities.

'The waters were dried up from off the earth,' as in Genesis 8:7, signifies the apparent dissipation of falsities.

(Riferimenti: Apocalypse Explained 17; Apocalypse Revealed 50; Genesis 8)