Healing is a sub-skill of waterbending which involves healing wounds by redirecting energy paths, or chi, throughout the body, using water as a catalyst. On rare occasions, waterbenders may instinctively be able to access this ability without any formal training and even be able to heal themselves.
After Avatar Aang ignored Jeong Jeong's warnings of recklessly firebending, he accidentally burned Katara due to a lack of control over his flames. Seeking to soothe the pain, Katara submerged her hands in a creek, only to see the water around her hands glow silvery-blue and heal her. Having accidentally discovered this new ability, Katara used it again later that day to heal a burn on Aang's forearm, after a fight with Zhao.
After the Hundred Year War, there were male healers as well. As Korra's waterbending teacher, Katara had also passed the art of healing onto Korra, and she used it to heal Bolin's shoulder after it was injured in the third round of the Fire Ferrets' semifinal match in the Pro-bending Tournament. She used the technique once more when she healed General Iroh's injury he sustained during his fight against the Equalists' attack on Republic City. When Korra had lost her bending due to Amon, she sought out Katara in order to be healed by her, but even she, known as the world's best healer, was unable to restore the Avatar's bending.
Healers are quite prominent in Republic City, and the best of them were visited by Tahno after his bending was taken from him by Amon. After Tarrlok fabricated evidence of a fight with the Equalists in City Hall, a healer was brought in to treat his arm, which he had used an electrified glove on to strengthen his alibi.
Following the Anti-bending Revolution, Kya healed her older brother, Bumi, who plunged down a waterfall while searching for Ikki. What was unique of her healing abilities was that neither she nor the water was in physical contact with Bumi. When Jinora's soul was trapped in the Spirit World, Kya and Katara tried to keep her physical body alive by keeping her energies flowing.
Physically, healing draws on the restorative properties of water in organisms that are primarily composed of it, such as human beings. Though unusually strong and powerful, waterbending-induced healing cannot heal every ailment, for example, Jet's internal wounds or the complications associated with Princess Yue's birth. It has been demonstrated that healing is ineffective on a person who has had their chi flow blocked or otherwise disrupted; Katara was unable to help a Terra Team member who had been a victim of Ty Lee's chi blocking skills, and not even the best healers could restore bending lost through advanced bloodbending, as demonstrated by failed attempts by Republic City's best healers to restore Tahno's, and Katara's to restore Korra's.
So far, waterbending induced healing is known to work on physical injuries, such as burns (Toph's feet and Katara's own hands), lacerations (Hakoda's injury during the Day of Black Sun), broken bones (Sokka's left arm), diseases brought on by severe pollution (Jang Hui villagers), and severe tissue damage caused by lightning bolts (Aang and Zuko); it is even able to cure mental distress and tampering (Jet). The healing abilities of a waterbender appear to be influenced by the water they use: when using spirit water from the Spirit Oasis in the North Pole, Katara was able to save Aang's life after he was mortally wounded from being struck by lightning (though he remained in a coma for a few weeks and required follow-up healing sessions to cope with the pain and be restored to full health).
In one aspect, the technique involves changing a spirit's negative energy into positive energy, restoring its internal balance in the process. It is performed by encircling a spirit in water and is completed when the spirit begins to glow bright yellow, at which point the spirit dissipates or assumes a pacified form. Although the technique has been used extensively to calm single spirits, it can also be used to calm several spirits simultaneously, as both Unalaq and Korra have demonstrated.
In another variation, the conversion process can be used to promote imbalance, by changing a spirit's positive energy into negative energy. The mechanics of the technique remain the same, although the spirit is covered by purple light instead of gold. Unalaq claims that this variation has the potential to destroy a human's soul.
- By 100 AG, all known healers were female due to the dissipation of the Southern Water Tribe waterbenders and the tradition of the Northern Water Tribe to restrict female benders to hone the vitakinetic sub-skill of waterbending. Males began to practice the art shortly after the end of the Hundred Year War, however, as male healers were present in both Republic City and the Northern Water Tribe.
- The only known instances of a healer using their abilities upon themselves is when Katara healed her own hands after they were burnt by Aang's firebending and when Korra healed herself after an earthbending match.
- A technique similar to healing was used by an elderly shaman in 171 AG and involved the use of firebending to sense chi paths and detect spiritual energy within an individual. In contrast to the waterbending form of healing, this technique does not revitalize any cells to accelerate healing.
- Korra is the only person known to have used both the regular and spiritual forms of healing. She is also the only known Avatar to have practiced healing.