Hai is the twelfth Earthly Branch, belonging to Yin Water, associated with the Pig zodiac sign, and corresponds to the Hai hour (9:00–11:00 p.m.). Hai Water represents early winter water, internally storing Ren Water and Jia Wood; its nature is profound and nurturing, symbolizing wisdom, inclusiveness, and abundance. Hai Water is the Place of Growth for Wood, indicating latent vitality.
Hai Water is identified from the Earthly Branches of the Four Pillars in a Bazi chart. If Hai appears in the Year Branch, the native belongs to the Pig zodiac; if Hai appears in the Day Branch, the Spouse Palace is Hai Water. Hai Water is strongest during Hai Month (the tenth lunar month).
A person born on a Gui Hai day has Hai Water as Friend in the Day Branch, suggesting a wise and compatible spouse who shares similar aspirations.