The Sea or the Water is an area of the sky in which many water-related, and few land-related, constellations occur. This may be because the Sun passed through this part of the sky during the rainy season.
Most of these constellations are named by Ptolemy:
Aquarius the Water-bearer
Capricornus the Sea-goat
Cetus the Whale
Delphinus the Dolphin
Eridanus the Great River
Hydra the Water serpent
Pisces the Fishes
Piscis Austrinus, the Southern Fish (not named by Ptolemy)
Sometimes included are the ship Argo and Crater the Water Cup.
Some water-themed constellations are newer, so are not in this region. They include Hydrus, the lesser water snake; Volans, the flying fish; and Dorado, the swordfish.