The manaia is a guardian representing balance and protection. Sky, earth and sea.
The new age understanding of the manaia is that it represents the balance between the sky, the earth and the sea. Its design is based on birds, which are seen as vehicles for the souls of the dead as they travel to the afterlife. Birds were so valued by Maori that their cries were listened to and their movements watched with care. As a result, all manaia serve as guardians and givers of omens. To wear one can protect from evil and connect the wearer with the souls of the dead. They are usually depicted in profile, and some feel this is because the manaia is half in the spiritual world and half in this world.
They were usually carved with grotesque figures, or as almost human with a fierce facial expression. To hear more about the mania design, you can listen to the below recording.
Another form which many class as a manaia is the pekapeka design. Pekapekas are said to represent New Zealand's native bat and are usually symmetrical with opposing snake-like heads.
The marakihau is another design many know as a manaia and has the form of a sea taniwha (sea monster). Some authors note that marakihau were spirits of ancestors that had taken up residence in the ocean. But unlike the bat form of the pekapeka, marakahui are depicted as mermen with sinuous bodies that terminate in curled tails, much like manaia.
Furthermore, there is a design known as the koropepe which many see as a relative of the manaia. It has a coiled snake or eel-like body and a large bird-like head. In traditional Maori society this design was extremely rare. Today it is usually set with a paua shell eye or the eye is filled with a red wax.