The purified river reaches the pond of The Moon, but the crayfish does not obey the current. It does not wish to go forward; it wants an ideal — symbolized by The Moon.
Jodorowsky reads the crayfish as the embodiment of idealistic, regressive desire that resists the forward flow of life and instead projects onto the lunar image a longing it cannot realise.
, The Way of Tarot: The Spiritual Teacher in the Cards, 2004thesis