According to Swedenborg, water in general represents natural truth, or the ideas we need to lead good lives on a relatively external level. Of course, water occurs in many different states — ice, snow, hail, rain, liquid, steam and vapor — which reflects and expresses the variety of forms and interactions those ideas can have.
Frost or hoar frost, Swedenborg says, represents ideas that are flowing out into good actions, because it is water that has been bonded into a single form as ice.
Passages from Swedenborg
Arcana Coelestia (Elliott) n. 8459
8459. ‘Tiny like hoar frost on the earth’ means truth in the form of good – uninterrupted and flowing. This is clear from the meaning of ‘tiny’ as a word having reference to truth, dealt with immediately above; and from the meaning of ‘like hoar frost’ as in the form of good. The good of truth, the good existing with a member of the spiritual Church, 8458, is compared to hoar frost because it forms more of a continuous sheet than snow. Consisting of tiny white flakes snow has reference to truth, while hoar frost, being the nearest thing to it, has reference to truth that has become good, which is the good of truth.