Capricorn the Sea Goat is one of the oldest constellations in the zodiac, located
in the area of the autumnal sky that since ancient times was associated to the
waters and called 'The Sea'. The old Babylonians, Egyptians and Chinese connected
Capricorn (Sumerian: 'goat fish') with the rainy season, the Aztecs saw it as a
Almost from its beginning Capricorn was seen as the personification of the Babylonian god Ea, who had the lower part half of a fish and the upper part of a goat. He was the god of the seas, as well as the god of knowledge, wisdom, magic and medical science, he lived in the ocean and came out every day to watch over the lands, hereby taken the body of a goat for easier walking on land. He brought culture and science to mankind, filled the rivers with fish and provided moisture to the earth to made the grain grow. At night he returned to the seas again.
The Sumerian equivalent for Ea was Enki, high god of the sweet waters and the intellect, of wisdom and medicine and the keeper of all secret and magical knowledge of life and immortality. Seen as a goat-fish in general, Enki entered the land in human appearance which showed him as a man with rivers flowing down from him.
The Egyptians kept the image of the sea goat, but associated Capricorn to Thoth as the god of wisdom as well as to Nun as the god of waters. Thoth won the contest for the constellation, mainly because his tasks as a god bringing knowledge, writing and wisdom to mankind matched Ea much better than the waters of Nun, which were rather seen as the primeval waters of chaos.
the Egyptian zodiac
The Greek mythology ignored the lower half of the Sea Goat and connected the
constellation to the nature god Pan, who lived in the woods and was seen as half
man, half goat. He was always after the nymphs, enjoyed himself playing pipes and
was famous for his outrageous character.
To match the image of the fish, a legend was formed in which Pan jumped into a river and tried to become a fish, but didn't succeed and stayed half a goat, so that Zeus was amused enough to place Pan in the sky. In another legend the constellation was seen as the goat nymph Amalthea who suckled Zeus as a baby, so he placed her in the sky later on to express his thanks.
That one of the most 'watery' water signs was made an earth sign later was most likely due to the efforts of astrologers to keep a harmonic order within the zodiac - three earth signs were demanded, so three were made in order of their place within the circle, appropriate or not.