'A whale,' as in Jeremiah 51:34, signifies people who possess the universal aspects of the knowledges of faith, as known, and apply them to evil purposes. 'Whales,' or 'great fishes,' are sometimes mentioned in the prophets, and are used to signify the universal aspects of knowledges

(References: Arcana Coelestia 42)

Being "filled" means being endowed with a spiritual quality. When the material in question is good -- water, food, people who represent good things, etc. -- it means getting a desire for good and an understanding of truth from the Lord. When the material is bad -- dust, flies, emotions like despair or terror, etc. -- it means being overwhelmed and enslaved by the desire for evil and the false, twisted logic that supports it. There are a number of references in the Bible to "filling the hand," which has a specific meaning and is dealt with separately.