When Momo and Appa were separated from Aang, Katara, and Sokka, they encountered Tho, who was a little short and chubby, and Due, who began hunting them down. Aang found Appa and Momo, thus preventing Tho and Due from eating them. Despite having just been attacked by the Avatar, the tribesmen were more than happy to find fellow waterbenders outside of the swamp in Aang and Katara. They later invited the team to dinner at a small settlement within the swamp.
Tho, Due, and Huu later helped with the initial land stage of the Invasion of the Fire Nation, but remained behind when the invasion force started scaling the volcano. When the eclipse ended, the Fire Nation deployed its airships. The airships proceeded to the beach to destroy the submarines. The three waterbenders tried to protect the submarines, but their efforts proved to be in vain. A bomb blew them down, but they survived. Like the rest of the adult fighters, Tho was held at a Fire Nation prison, but was released at the end of the Hundred Year War, and later attended Fire LordZuko's coronation.
Tho was a simple man who loved living in the swamp. He was one of the smarter members of his tribe, and was usually the one instructing Due and the others on what to do. Like Due, he cared for his tribe and wanted what was best for everyone. Tho was a hospitable person and was more than happy to have a few visitors over for dinner.
Tho was a powerful and strong waterbender, being a Foggy Swamp Tribe member. He proved his skills several times, in both the swamp and during the Invasion of the Fire Nation. Tho also was a master of the rigid and stiff Foggy Swamp waterbending style.