Wikipedia
The Likanaya is a female creature originating in Australian Aboriginal mythology.
It is a creature similar to the typical mermaid in appearance, and has seaweed for hair. Seaweed that floats up to the water's surface is said, by natives, to come from the head of a likanaya.
Though, while this creature's normal form has the upper body of a humanoid female, and the lower part of a fish, it is also capable of shapeshifting. Among its favored forms are that of a crocodile, dragonfly, snake or swordfish.
Another power the likanaya was believed to possess includes the ability to manipulate the weather, such as bringing nourishing rain, or sending storms on those who make them angry.
With the abilities these spirits possess, some natives claim that they are the daughters and/or female counterparts (and thus wives) of the Rainbow Serpent Creator god, Ngalyod.