Iconographic representations of Goddess Ganga vary from region to region. Local traditions depict Murti, or idol, of Goddess Ganga based on their local beliefs. In Hindu Temples, river Goddess Ganga is depicted as a young maiden. She holds an overflowing pot of water. She travels on an aquatic animal known as Makara – similar to crocodile. Symbolically, this murti conveys the idea of abundance and fertility, which nourishes the living beings.
In some images Goddess Ganga is also represented as a mermaid wearing a crown and bearing on her forhead markings of sacred ash. In this form She is associated with Shiva.
In some images she is depicted as a beautiful woman with the lower half of the body being flowing water. This symbolizes her cleansing and purifying attributes.
Her popular emblems are water pot, flying whist and lotus.
Her Vahana or Vehicle is Makara – a hybrid aquatic animal – it has the body of a crocodile, tail of a fish with feathery fronds, depicting vegetation. Sometimes it also has an elephant like trunk. It symbolically represents the life-affirming qualities of waters and vegetation as well as the wisdom of earth and the sea.
Notes taken from book titled - Kamandalu: The Seven Sacred Rivers of Hinduism