Asmat spirit canoes (wuramon) are ceremonial carvings in the form of supernatural vessels. Wuramon are created for only a single use during emak cem ("the bone house feast"), a ceremony that celebrates the spirits of the recently dead and the initiation of young boys. After being secluded within a ritual house for several months, the boys emerge one by one and crawl across the wuramon, which is placed just outside the door, on their bellies. As each crosses the vessel, he is symbolically transformed from a boy to a man. Once across, he is seized by a man who cuts designs into his body that heal into permanent scarification patterns that mark him as an adult. Girls are similarly scarified at the same time, although they do not undergo seclusion. Once the ceremony is over, the wuramon, its purpose served, is discarded.
Crewed by spirits, the wuramon has no bottom, as spirits do not require a complete hull for their journey. The spirit figures have a dual nature. Their outer forms portray supernatural creatures, but each is named for a specific individual who has recently died, whose spirit it embodies. A turtle (mbu), considered a potent fertility symbol because of the numerous eggs it lays, appears near the center of this wuramon. Behind it is an okom, a dangerous water spirit. The other figures, gazing down through the bottomless hull, represent dangerous water spirits (ambirak), or humanlike spirits (etsjo). The prow depicts a hammerhead shark.