Night sea journey:
An archetypal motif in mythology, psychologically associated with depression and the loss of energy characteristic of neurosis.
The night sea journey is a kind of descensus ad inferos–a descent into Hades and a journey to the land of ghosts somewhere beyond this world, beyond consciousness, hence an immersion in the unconscious.["The Psychology of the Transference," CW 16, par. 455.]
Mythologically, the night sea journey motif usually involves being swallowed by a dragon or sea monster. It is also represented by imprisonment or crucifixion, dismemberment or abduction, experiences traditionally weathered by sun-gods and heroes: Gilgamesh, Osiris, Christ, Dante, Odysseus, Aeneas. In the language of the mystics it is the dark night of the soul.
Jung interpreted such legends symbolically, as illustrations of the regressive movement of energy in an outbreak of neurosis and its potential progression.
The hero is the symbolical exponent of the movement of libido. Entry into the dragon is the regressive direction, and the journey to the East (the “night sea journey”) with its attendant events symbolizes the effort to adapt to the conditions of the psychic inner world. The complete swallowing up and disappearance of the hero in the belly of the dragon represents the complete withdrawal of interest from the outer world. The overcoming of the monster from within is the achievement of adaptation to the conditions of the inner world, and the emergence (“slipping out”) of the hero from the monster’s belly with the help of a bird, which happens at the moment of sunrise, symbolizes the recommencement of progression.["On Psychic Energy," CW 8, par. 68.]
All the night sea journey myths derive from the perceived behavior of the sun, which, in Jung’s lyrical image, “sails over the sea like an immortal god who every evening is immersed in the maternal waters and is born anew in the morning.["Symbols of the Mother and of Rebirth,"CW 5, par. 306.] The sun going down, analogous to the loss of energy in a depression, is the necessary prelude to rebirth. Cleansed in the healing waters (the unconscious), the sun (ego-consciousness) lives again.