In Catalan mythology an aloja, also known as dona d'aigua is a feminine being that lives in places with fresh water. These "water-women" are said to be able to turn into water blackbirds. these women are not immortal, but can live for thousands of years and retain their youth. They are said to appear as small and innocent women, with a high self-esteem and very prideful of their beauty. They are good women and try to bring wealth and well-being to the areas they live in.

According to myth, water-women are nocturnal; have shimmering gold or red hair, and emerald or deep blue eyes; wear fine, rich clothes; and enjoy viewing their reflections in lakes on full-moon nights. Some of them are said to have beautiful wings of various colors. Many are said to carry magic wands carved from hazel, which is considered to be the only wood capable of casting spells.