Korean Flood myths (Starting a new race of humans) from wikipedia
Namu Doryeong
Namu Doryeong (Hangul: 나무도령) is a myth about the son of a guardian tree spirit. The son, Namu Doryeong, survived a flood by floating on the tree. He first saved a colony of ants from the flood, then a swarm of mosquitoes, until he had saved all the animals of the world. Namu Doryeong finally saved a young human boy, despite the tree's advice against it.
After the flood, Namu Doryeong met an older woman and her two daughters on Mt. Baekdu, where they had been safe from the flood. The woman told Namu Doryeong if he won a contest, he could have her daughter's hand in marriage. Namu Doryeong won the contest with the aid of a swarm of ants, who turned out to be the very ants that Namu Doryeong had saved during the flood. Namu Doryeong and the human boy married the −two daughters, and they formed the next race of humans